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Prevalence of the Metabolic Syndrome among Korean Workers by Occupational Group: Fifth Korean National Health and Nutrition Examination Survey (KNHANES) 2010
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Research Article Prevalence of the Metabolic Syndrome among Korean Workers by Occupational Group: Fifth Korean National Health and Nutrition Examination Survey (KNHANES) 2010
Ji Young Ryu1, Sukwoo Hong1, Chang-Hyo Kim2, Sangyoon Lee1, Jeong-Ho Kim3, Jong-Tae Lee3, Dae Hwan Kim1
Annals of Occupational and Environmental Medicine 2013;25:13-13.
DOI: https://doi.org/10.1186/2052-4374-25-13
Published online: August 5, 2013

1Department of Occupational and Environmental Medicine, Inje University Haeundae Paik Hospital, 875 Heaundae-ro, Haeundae-Gu, Busan 612-862, South Korea

2Inje University Graduate School, 197 Inje-ro, Gimhae, Gyungnam, South Korea

3Department of Occupational and Environmental Medicine, College of Medicine & Institute of Environmental and Occupational Medicine, Inje University, 75 Bokji-ro Busanjin-gu, Busan, South Korea

• Received: April 5, 2013   • Accepted: July 1, 2013

Copyright © 2013 Ryu et al.; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  • Objectives
    The prevalence of the metabolic syndrome has increased rapidly in South Korea over the past 10 years. However, the occurrence of the metabolic syndrome in workers grouped according to the specific type of work is not well understood in Korea. In this study, we assessed the differences in the prevalence of the metabolic syndrome by occupational group and evaluated the risk of the metabolic syndrome among occupational groups.
  • Methods
    From the Fifth Korean National Health and Nutrition Examination Survey (2010), 3,303 employed participants were included in this study. The unadjusted and age-adjusted prevalences of the metabolic syndrome were estimated and multiple logistic regression analysis was conducted using the presence of the metabolic syndrome as a dependent variable, and adjusting for age, education level, household income, drinking behavior, smoking status, physical activity, work hours, and work scheduling pattern.
  • Results
    Among male workers, non-manual workers had the greatest age-adjusted prevalence (26.4%, 95% CI: 22.3-30.5%) among the occupational groups. In a logistic regression analysis, male manual workers had a significantly lower odds ratio for the metabolic syndrome relative to non-manual workers (0.59, 95% CI: 0.41-0.85).
  • Conclusion
    Our study demonstrated differences in the prevalence of the metabolic syndrome by occupational group and identified the greatest risk for the metabolic syndrome in male non-manual workers.
The metabolic syndrome is a condition that is defined by the combination of five factors: abdominal obesity, hypertension, hypertriglyceridemia, low HDL-cholesterol level, and hyperglycemia [1]. These components of the metabolic syndrome are major risk factors for cardiovascular disease and impaired glucose metabolism [1-4].
Recently, the prevalence of the metabolic syndrome has increased rapidly in South Korea [5,6]. According to a study using the data from the Korean National Health and Nutrition Examination Survey (KNHANES), the age-adjusted prevalence of the metabolic syndrome in 2007 was 31.3%, while the age-adjusted prevalence of the metabolic syndrome in 1998 had been just 24.9% [6]. It is thought that the rapid increase in the prevalence of the metabolic syndrome may have arisen from lifestyle changes including a westernized diet and physical inactivity [5-7].
On the other hand, recent studies have shown that the prevalence of the metabolic syndrome varies in different occupational groups [8,9]. Among U.S. workers, the unadjusted and age-adjusted prevalences of the metabolic syndrome were greatest in “transportation and material occupations” and “food preparation and food service workers,” respectively [9]. In male Spanish workers, the highest age-adjusted prevalence of the metabolic syndrome was found among “machine installers, operators and assemblers” while the prevalence of the metabolic syndrome in female workers was highest among “skilled workers in the agricultural and fishing industries” [8]. It is expected that the prevalence of the metabolic syndrome among workers may differ by country, considering the distinctive working environment of each country. In Korea, only a few studies have assessed the association between the occupational group and the metabolic syndrome. Although previous research by Myoung et al. has evaluated the relationship between occupations and the metabolic syndrome among Korean workers, the study was limited by the fact that the occupations were grouped into manual or non-manual workers only, without considering service and sales workers as a separate work group [10].
In this study, we assessed the differences in the prevalence of the metabolic syndrome and its individual criteria by occupational group and evaluated the risk of the metabolic syndrome among occupational groups using KNHANES data.
Subjects
Data from the fifth KNHANES, gathered in 2010, was used for the analyses. The KNHANES is a multistage stratified complex design survey of a representative sample of the entire Korean population conducted by the Korea Centers for Disease Control and Prevention. The total number of participants was 8,958, and the participation rate was 81.9%. Trained interviewers and laboratory technicians conducted surveys in households, including administering questionnaires, performing health examinations, and collecting blood samples. Subjects who were at least 20 years old, who reported having jobs, and who had occupational information were included in this study (n = 3,667). Subjects who reported having no jobs (n = 4,595), who had no occupational information (n = 597), or who belonged to the armed forces group in the occupational classification (n = 31) were excluded from this study. After this exclusion, the workers who were aged below 20 years old were also excluded (n = 68). Among 3,667 included workers, 3,303 workers who had fully available data needed for diagnosis of the metabolic syndrome were analyzed. This study was approved by the Institutional Review Board of the Haeundae Paik Hospital.
Occupational classification
The subjects were classified into nine occupational subgroups based on the KNHANES data. The KNHANES employed the major categories of the Korean Standard Classification of Occupations (KSCO) [11] as the occupational classification. These occupations were grouped into three categories according to their degree of physical work: non-manual workers, service/sales workers, and manual workers. Non-manual workers were managers, professionals and related workers, and clerks. Service workers and sales workers constituted one distinctive group. Manual workers consisted of skilled agricultural, forestry and fishery workers, craft and related trades workers, equipment, machine operating and assembling workers, and elementary workers.
Definition of the metabolic syndrome
The presence of the metabolic syndrome was determined by the consensus definition [1] incorporating International Diabetes Federation (IDF) worldwide criteria [12] and American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI) criteria [13]. An individual who had any three or more of the following five criteria was defined as having the metabolic syndrome: 1) waist circumference ≥ 90 cm in men and ≥ 80 cm in women, 2) blood pressure ≥ 130/85 mmHg or receiving anti-hypertensive medication, 3) triglycerides ≥ 150 mg/dl, 4) HDL-cholesterol < 40 mg/dl in men and < 50 mg/dl in women, 5) fasting glucose ≥ 100 mg/dl or taking blood glucose lowering drugs.
Covariates
Age, level of education, household income, smoking status, high-risk drinking behavior, vigorous physical activity, work hours, work scheduling pattern, and body mass index (BMI) were included as covariates in this study. The levels of education were categorized into elementary school graduates (6-year course), middle school graduates (3-year), high school graduates (3-year), and some university education or above (2 or more years). Household income was classified by quartile as low, low-middle, middle-high, or high levels. Smoking status was divided into non-smokers, ex-smokers, and current smokers. High-risk drinking was defined as at least 7 glasses per day in men and at least 5 glasses per day in women and drinking behavior was categorized into no, once a month, once a week, or every day experience of high-risk drinking. Vigorous physical activity was defined as physical activities over 10 minutes that are more strenuous than usual activities or make one breathless, including carrying heavy loads, running, climbing, fast cycling, fast swimming, soccer, basketball, and so on. This variable was divided into none, below 5 days per week, and at least 5 days per week of vigorous physical activities. Work hours were categorized into 40 hours per week or less and over 40 hours per week. Work schedule patterns were grouped as either daytime fixed work or non-daytime work, including night-time and shift work. BMI was classified into normal/underweight (below 25 kg/m2), overweight (between 25 and 30 kg/m2), and obese (more than 30 kg/m2).
Statistical analyses
The statistical analyses were performed using SAS Enterprise Guide (version 4.2; SAS Institute Inc., Cary, NC) to take into account sample weights and complex sample design effects. All of the data are presented as an estimated percentage (standard error) or estimated mean (standard error) for the demographic variables and each component of the metabolic syndrome. The Rao-Scott chi-squared test was used to compare the prevalence of the categorical variables. The unadjusted and age-adjusted prevalences of the metabolic syndrome for nine occupational groups were estimated. Age-standardization by the direct method was done for the prevalence estimates using 2010 Census population data of Korea. The prevalence estimate for each occupational group was considered significantly higher than that for workers overall if the estimate was above the upper bounds of the 95% confidence interval for the overall prevalence estimate [14]. For the occupational groups, multiple logistic regression analysis was conducted with the presence of the metabolic syndrome as a dependent variable after stratification for gender. The multiple logistic regression analysis was performed, adjusting for age (continuous variable), level of education, household income, drinking behavior, smoking status, physical activity, work hours, and work schedule pattern.
Tables 1 and 2 present the demographic characteristics by the major job categories of the KSCO among male and female workers, respectively. In both the male and female workers, “managers”, “professional and related” workers, and “clerks” had high levels of education and household income. Among the male workers, the proportion doing vigorous physical activity at least 5 days per week was lowest in the “managers” (3.5%), followed by “professional and related” workers (3.8%) and “clerks” (5.8%) and highest in the “skilled agricultural, forestry and fishery workers” (17.5%), followed by “elementary” workers (14.8%), sales workers (12.7%), and service workers (12.3%). The proportion of those with less than 40 work hours per week was higher in the “managers” (48.4%), “professional and related” workers (41%), and “clerks” (42.6%) than in the other work groups in the men. Service workers reported the highest proportion of non-day work in both the male (51.4%) and female (29.8%) workers. “Managers”, “professional and related” workers, and “clerks” were more likely to be overweight or obese than those of the other occupational groups in the male workers. On the other hand, in female workers, the proportion of overweight or obese individuals was smaller among the “managers”, “professional and related” workers, and “clerks” than the other occupational groups.
Table 1
Demographic characteristics by major category of the Korean Standard Classification of Occupations among male workers
  Managers Professional and related workers Clerks Service workers Sales workers Skilled agricultural, forestry and fishery workers Craft and related trades workers Equipment, machine operation and assembling workers Elementary workers Total p-value
Age (years)*
50.9 (1.3)
38.2 (0.7)
39.1(0.7)
36.8 (1.4)
41.2 (1.2)
56.4 (1.4)
42.7 (0.9)
45.1 (1.1)
46.1 (1.7)
44.1 (0.4)
< 0.001
Education
 
 
 
 
 
 
 
 
 
 
< 0.001
  ≤ Elementary school
0.0 (0.0)
0.6 (0.4)
0.4 (0.4)
4.9 (2.1)
6.5 (2.1)
41.5 (3.3)
14.2 (2.7)
7.7 (1.8)
21.7 (4.3)
10.7 (1.1)
 
  Middle school
16.3 (5.6)
0.4 (0.3)
1.7 (1.0)
6.4 (2.4)
7.6 (2.2)
20.8 (3.9)
13.9 (2.5)
19.7 (3.0)
17.5 (3.6)
10.3 (0.9)
 
  High school
31.8 (6.7)
21.0 (3.6)
27.6 (3.4)
56.3 (5.4)
45.7 (4.4)
24.9 (3.2)
53.3 (4.0)
56.9 (4.0)
50.5 (4.9)
39.2 (1.5)
 
  ≥ University
51.8 (6.7)
78.0 (3.6)
70.3 (3.6)
32.4 (4.8)
40.2 (3.9)
12.8 (2.8)
18.6 (3.0)
15.7 (3.2)
10.3 (2.8)
39.8 (1.7)
 
Household income
 
 
 
 
 
 
 
 
 
 
< 0.001
  Low
3.7 (2.7)
6.7 (1.8)
2.7 (1.1)
6.5 (2.7)
9.3 (2.2)
24.1 (4.0)
12.3 (2.8)
8.6 (2.4)
26.5 (4.2)
10.9 (1.0)
 
  Low-middle
10.6 (4.4)
17.1 (2.7)
24.5 (2.8)
34.6 (2.7)
27.6 (3.6)
28.2 (4.3)
35.4 (3.7)
26.9 (3.5)
29.2 (4.3)
26.4 (1.4)
 
  Middle-high
29.2 (7.2)
39.0 (3.0)
33.9 (3.1)
25.0 (4.4)
36.1 (4.3)
18.2 (2.6)
29.0 (3.4)
37.6 (3.6)
29.5 (4.9)
31.9 (1.4)
 
  High
56.5 (6.1)
37.3 (2.9)
38.9 (3.7)
33.9 (5.2)
27.0 (3.7)
29.5 (4.2)
23.4 (3.3)
26.9 (3.4)
14.8 (3.6)
30.7 (1.6)
 
High-risk drinking
 
 
 
 
 
 
 
 
 
 
0.002
  Never
17.5 (5.2)
12.7 (2.1)
14.1 (2.3)
7.4 (2.6)
13.0 (2.7)
18.1 (3.6)
14.1 (2.5)
14.8 (2.3)
26.4 (4.6)
14.8 (1.0)
 
  Once a month
13.4 (6.3)
46.3 (3.4)
38.9 (3.3)
44.4 (5.8)
33.7 (4.0)
32.6 (4.3)
42.5 (4.5)
39.2 (4.3)
35.9 (5.5)
40.0 (1.5)
 
  Once a weak
30.0 (6.6)
30.2 (3.2)
38.3 (3.6)
35.5 (5.3)
43.6 (4.3)
26.2 (4.1)
28.8 (3.8)
29.7 (3.5)
20.2 (4.7)
31.8 (1.2)
 
  Everyday
9.1 (4.2)
10.7 (2.0)
8.7 (2.2)
12.7 (3.6)
9.8 (2.6)
23.2 (3.3)
14.6 (2.7)
16.3 (3.2)
17.5 (4.0)
13.4 (1.1)
 
Smoking status
 
 
 
 
 
 
 
 
 
 
0.027
  Non-smoker
15.0 (4.4)
23.7 (2.4)
17.7 (2.6)
18.7 (3.9)
17.9 (3.1)
13.9 (2.8)
12.0 (2.4)
10.9 (2.5)
15.5 (3.9)
16.5 (1.0)
 
  Ex-smoker
41.1 (6.1)
30.1 (2.9)
31.6 (2.8)
23.9 (4.4)
31.8 (3.7)
41.8 (3.0)
32.7 (3.6)
34.4 (3.1)
29.5 (4.3)
32.6 (1.3)
 
  Current smoker
43.9 (6.0)
46.3 (3.4)
50.8 (2.9)
57.4 (5.1)
50.3 (4.4)
44.3 (3.5)
55.4 (3.7)
54.7 (3.4)
55.0 (5.3)
50.9 (1.4)
 
Vigorous physical activity
 
 
 
 
 
 
 
 
 
 
< 0.001
  None
66.2 (6.4)
53.3 (3.8)
44.4 (3.6)
52.1 (5.1)
50.2 (3.5)
60.7 (3.3)
53.3 (4.2)
49.4 (3.7)
58.8 (5.2)
52.7 (1.4)
 
  < 5 days per week
30.3 (6.1)
42.8 (3.9)
49.7 (3.6)
35.7 (5.2)
37.1 (4.1)
21.8 (2.8)
36.1 (4.1)
41.4 (3.7)
26.4 (5.2)
37.6 (1.4)
 
  ≥ 5 days per week
3.5 (2.1)
3.8 (1.2)
5.8 (1.4)
12.3 (3.6)
12.7 (3.0)
17.5 (2.6)
10.7 (2.2)
9.2 (2.4)
14.8 (4.1)
9.7(0.8)
 
Work hours
 
 
 
 
 
 
 
 
 
 
< 0.001
  ≤ 40 hours per week
48.8 (6.5)
41.0 (3.6)
42.6 (3.3)
28.5 (4.7)
28.3 (3.9)
37.8 (4.4)
25.6 (2.9)
23.6 (3.2)
39.4 (4.8)
34.4 (1.3)
 
  > 40 hours per week
51.2 (6.5)
59.0 (3.6)
57.4 (3.3)
71.5 (4.7)
71.7 (3.9)
62.2 (4.4)
74.4 (2.9)
76.4 (3.2)
60.6 (4.8)
65.6 (1.3)
 
Work schedule pattern
 
 
 
 
 
 
 
 
 
 
< 0.001
  Day
92.0 (4.5)
81.7 (2.5)
90.9 (2.2)
48.6 (5.7)
84.8 (3.0)
99.8 (0.2)
87.2 (3.5)
72.9 (3.3)
68.5 (4.1)
82.2 (1.2)
 
  Night/overnight
3.7 (2.0)
13.6 (2.3)
2.6 (1.1)
26.3 (5.3)
14.2 (3.0)
0.1 (0.1)
2.0 (1.3)
8.7 (2.0)
11.3 (2.8)
8.6 (0.8)
 
  Shift
0.0
1.5 (0.9)
5.2 (1.9)
15.5 (4.1)
0.3 (0.2)
0.0
8.4 (2.7)
11.3 (2.5)
19.4 (3.2)
6.3 (0.8)
 
  Others
4.2 (4.1)
3.2 (1.0)
1.3 (0.7)
9.6 (2.7)
0.7 (0.5)
0.1 (0.1)
2.4 (2.0)
7.1 (2.2)
0.8 (0.7)
2.9 (0.5)
 
BMI category
 
 
 
 
 
 
 
 
 
 
0.230
  Normal/underweight
55.2 (7.6)
56.6 (3.0)
58.1 (3.5)
60.5 (5.8)
62.8 (4.2)
68.5 (3.5)
61.4 (3.3)
62.2 (3.7)
67.0 (4.5)
61.3 (1.4)
 
  Overweight
37.5 (6.4)
39.3 (2.9)
36.4 (3.6)
37.7 (5.7)
30.5 (3.7)
30.8 (3.4)
35.2 (3.2)
33.5 (3.6)
30.1 (4.5)
34.7 (1.3)
 
  Obese 7.3 (3.7) 4.1 (1.3) 5.5 (1.7) 1.8 (1.3) 6.7 (2.0) 0.7 (0.5) 3.4 (1.5) 4.3 (1.5) 2.9 (1.4) 3.9 (0.6)  
*Estimated mean (standard error).
Table 2
Demographic characteristics by major category of the Korean Standard Classification of Occupations among female workers
  Managers Professional and related workers Clerks Service workers Sales workers Skilled agricultural, forestry and fishery workers Craft and related trades workers Equipment, machine operation and assembling workers Elementary workers Total p-value
Age (yr)*
54.1 (3.9)
34.2 (0.6)
33.7 (0.7)
43.2 (1.0)
43.2 (1.0)
57.4 (1.5)
49.1 (2.9)
41.8 (2.4)
51.7 (1.0)
45.4 (0.6)
< 0.001
Education
 
 
 
 
 
 
 
 
 
 
< 0.001
  ≤ Elementary school
0.0 (0.0)
0.6 (0.3)
0.3 (0.3)
21.7 (3.3)
18.4 (2.6)
67.2 (4.7)
30.4 (9.7)
16.5 (7.4)
39.8 (3.0)
22.3 (1.9)
 
  Middle school
18.2 (15.1)
0.6 (0.4)
2.2 (1.0)
18.3 (2.9)
13.3 (2.5)
15.5 (4.5)
34.5 (8.4)
17.2 (7.6)
18.5 (3.4)
11.6 (1.1)
 
  High school
18.4 (12.9)
17.1 (2.5)
50.1 (3.9)
47.3 (3.6)
47.6 (3.7)
15.0 (4.2)
31.8 (7.6)
60.4 (10.3)
34.7 (3.7)
34.5 (1.7)
 
  ≥ University
63.3 (18.0)
81.7 (2.5)
47.4 (4.1)
12.6 (2.7)
20.7 (3.0)
2.3 (1.4)
3.3 (2.3)
5.8 (4.1)
6.9 (1.8)
31.5 (1.8)
 
Household income
 
 
 
 
 
 
 
 
 
 
< 0.001
  Low
0.0 (0.0)
4.0 (1.4)
2.6 (1.2)
10.0 (2.3)
12.1 (2.3)
35.7 (4.9)
30.6 (9.4)
0.0 (0.0)
25.1 (2.9)
14.2 (1.3)
 
  Low-middle
1.2 (1.2)
17.2 (2.7)
20.7 (3.8)
31.1 (3.6)
23.0 (3.8)
25.6 (3.2)
23.6 (6.1)
23.9 (7.7)
36.9 (3.4)
25.4 (1.5)
 
  Middle-high
14.6 (13.3)
37.4 (3.3)
36.8 (4.2)
30.7 (3.8)
35.4 (3.8)
18.0 (3.3)
28.2 (7.6)
45.2 (10.9)
22.6 (2.5)
30.8 (1.5)
 
  High
84.2 (13.4)
41.4 (3.4)
40.0 (3.8)
28.2 (3.3)
29.6 (3.7)
20.7 (3.2)
17.6 (6.5)
30.9 (9.5)
15.4 (2.6)
29.6 (1.6)
 
High-risk drinking
 
 
 
 
 
 
 
 
 
 
< 0.001
  Never
77.4 (15.6)
39.6 (3.5)
31.7 (3.9)
35.9 (3.9)
43.6 (3.8)
57.0 (5.4)
18.5 (6.7)
37.1 (11.3)
42.7 (5.0)
39.8 (1.7)
 
  Once a month
22.6 (15.6)
45.0 (3.7)
52.9 (4.3)
43.5 (4.0)
37.8 (4.2)
38.4 (4.4)
58.6 (9.3)
59.8 (11.7)
35.9 (3.9)
43.6 (4.6)
 
  Once a weak
0.0 (0.0)
15.4 (3.2)
14.7 (3.0)
13.6 (2.6)
17.2 (3.3)
4.0 (2.2)
19.5 (8.5)
3.1 (3.1)
14.3 (3.3)
13.8 (1.3)
 
  Everyday
0.0 (0.0)
0.0 (0.0)
0.7 (0.7)
7.0 (2.0)
1.3 (1.3)
0.6 (0.6)
3.4 (2.6)
0.0 (0.0)
7.1 (3.0)
2.7 (0.6)
 
Smoking status
 
 
 
 
 
 
 
 
 
 
0.015
  Non-smoker
100.0 (0.0)
88.5 (1.9)
86.3 (2.7)
86.0 (3.1)
83.4 (3.0)
96.4 (1.7)
91.8 (5.6)
96.7 (3.3)
83.0 (3.2)
87.4 (1.2)
 
  Ex-smoker
0.0 (0.0)
7.5 (1.6)
7.9 (2.2)
4.9 (1.7)
9.5 (2.4)
2.3 (1.4)
8.0 (5.6)
0.0 (0.0)
5.4 (1.7)
6.3 (0.8)
 
  Current smoker
0.0 (0.0)
4.0 (1.1)
5.8 (1.8)
9.2 (2.9)
7.1 (2.2)
1.3 (0.8)
0.1 (0.1)
3.3 (3.3)
11.6 (3.1)
6.3 (0.9)
 
Vigorous physical  activity
 
 
 
 
 
 
 
 
 
 
0.007
  None
55.8 (18.7)
74.1 (3.1)
70.2 (3.7)
70.1 (3.7)
69.5 (3.8)
76.1 (4.1)
86.3 (5.4)
61.5 (8.8)
75.0 (3.2)
72.9 (1.4)
 
  < 5 days per week
44.2 (18.7)
21.8 (2.9)
26.2 (3.6)
20.4 (3.6)
23.7 (3.3)
11.4 (2.7)
6.5 (3.6)
23.9 (8.4)
16.2 (2.4)
19.8 (1.2)
 
  ≥ 5 days per week
0.0 (0.0)
4.1 (1.3)
3.6 (1.4)
9.5 (2.3)
6.8 (2.0)
12.5 (3.3)
7.2 (4.3)
14.6 (5.6)
8.8 (2.0)
7.3 (0.8)
 
Work hours
 
 
 
 
 
 
 
 
 
 
< 0.001
  ≤ 40 hours per week
80.4 (13.9)
57.0 (3.5)
52.4 (4.2)
33.7 (4.0)
48.9 (4.0)
50.9 (4.0)
29.4 (7.3)
35.9 (9.9)
64.5 (3.6)
51.2 (1.6)
 
  > 40 hours per week
19.6 (13.9)
43.0 (3.5)
47.6 (4.2)
66.3 (4.0)
51.1 (4.0)
49.1 (4.0)
70.6 (7.3)
64.1 (9.9)
35.5 (3.6)
48.8 (1.6)
 
Work schedule pattern
 
 
 
 
 
 
 
 
 
 
<0.001
  Day
93.8 (5.4)
74.8 (3.2)
94.3 (2.0)
70.2 (3.7)
77.7 (3.4)
99.0 (0.7)
93.0 (4.6)
74.2 (9.6)
85.8 (2.7)
82.7 (1.5)
 
  Night/overnight
5.1 (5.1)
18.9 (3.0)
3.2 (1.5)
24.5 (3.4)
15.6 (2.9)
0.0
4.6 (2.6)
6.1 (3.8)
12.0 (2.6)
12.9 (1.3)
 
  Shift
1.1 (1.2)
3.8 (1.5)
1.7 (1.3)
2.2 (0.9)
3.7 (1.7)
0.3 (0.3)
2.4 (2.4)
8.1 (6.1)
1.2 (0.6)
2.4 (0.5)
 
  Others
0.0
2.5 (1.0)
0.7 (0.5)
3.1 (1.2)
3.0 (1.4)
0.7 (0.6)
0.0
11.6 (9.0)
1.0 (0.5)
2.0 (0.4)
 
BMI category
 
 
 
 
 
 
 
 
 
 
0.009
  Normal/underweight
82.8 (11.7)
82.9 (2.5)
79.7 (3.2)
72.2 (3.2)
68.5 (4.0)
66.8 (4.4)
69.4 (8.0)
70.3 (9.6)
70.9 (2.6)
74.2 (1.3)
 
  Overweight
17.2 (11.7)
14.5 (2.2)
15.0 (2.6)
22.5 (3.0)
27.6 (4.0)
26.4 (3.3)
30.5 (8.0)
17.3 (7.8)
24.4 (2.7)
21.2 (1.1)
 
  Obese 0.0 (0.0) 2.6 (1.2) 5.2 (1.9) 5.3 (1.8) 3.9 (1.5) 6.8 (1.9) 0.1 (0.1) 12.4 (7.0) 4.7 (1.3) 4.5 (0.7)  
*Estimated mean (standard error).
The prevalence estimates of the metabolic syndrome by demographic characteristics stratified by gender are shown in Table 3. Among the male workers, the subgroup with the highest prevalence of the metabolic syndrome was the obese group (68.3%), followed by the overweight group (39.1%) and the group engaging in high-risk drinking everyday (38.1%). In the female workers, the group of those aged ≥ 70 years (53.5%) showed the highest prevalence of the metabolic syndrome, followed by the obese group (46.1%).
Table 3
The prevalence of the metabolic syndrome according to demographic characteristics
 
Male
Female
Demographics Number *† Prevalence (95% confidence intervals) Number *† Prevalence (95% confidence intervals)
Age group
 
 
 
 
  20–29 years
152/1,942,533
9.2 (4.1–14.3)
231/1,733,502
3.5 (0.7–6.2)
  30–39 years
428/3,276,013
17.8 (13.5–22.1)
291/1,634,571
5.5 (2.0–9.0)
  40–49 years
477/3,659,709
25.9 (21.3–30.4)
371/2,433,142
12.5 (8.2–16.8)
  50–59 years
392/2,681,787
35.7 (30.2–41.2)
374/1,891,022
30.8 (25.2–36.5)
  60–69 years
297/1,176,249
36.4 (29.5–43.3)
188/758,966
38.0 (30.1–45.8)
  ≥ 70 years
113/415,885
17.4 (9.1–25.8)
93/373,407
53.5 (43.5–63.4)
Education
 
 
 
 
  ≤ Elementary school
262/1,377,314
28.7 (21.5–35.8)
407/1,912,522
40.9 (35.6–46.2)
  Middle school
218/1,385,292
35.9 (29.0–42.8)
175/989,224
24.4 (16.6–32.3)
  High school
637/5,078,713
20.1 (16.4–23.7)
491/3,089796
9.3 (6.1–12.5)
  ≥ University
742/5,310,859
23.6 (19.9–27.4)
481/2,833,069
7.6 (4.2–11.1)
Household income
 
 
 
 
  Low
224/1,362,396
25.9 (18.9–32.9)
239/1,171,008
35.3(28.6–41.9)
  Low–middle
476/3,488,782
21.4 (16.9–25.8)
366/2,177,822
19.8 (15.3–24.2)
  Middle–high
568/4,173,072
23.8 (19.4–28.2)
448/2,712,764
14.3 (10.7–18.0)
  High
575/4,051,739
25.5 (21.1–29.9)
481/2,648,160
10.4 (7.1–13.7)
High–risk drinking
 
 
 
 
  Never
275/1,681,687
14.7 (9.6–19.9)
473/2,633,998
15.4 (11.2–19.7)
  Once a month
644/4,713,082
21.2 (17.4–24.9)
494/2,956,125
12.8 (9.3–16.4)
  Once a weak
490/3,727,662
26.0 (21.6–30.4)
130/932,867
17.4 (9.6–25.2)
  Everyday
226/1,602,909
38.1 (30.7–45.5)
23/152,018
31.1 (8.8–53.4)
Smoking status
 
 
 
 
  Non–smoker
320/2,194,133
19.5 (14.4–24.5)
1,394/7,721,944
17.5 (14.9–20.2)
  Ex–smoker
697/4,369,598
27.0 (22.9–31.0)
81/546,406
16.0 (7.0–25.0)
  Current smoker
841/6,585,245
23.7 (20.1–27.3)
78/547,078
15.8 (6.7–24.9)
Vigorous physical activity
 
 
 
 
  None
1,035/6,872,680
25.0 (21.9–28.1)
1,144/6,444,936
17.8 (14.4–20.7)
  < 5 days per week
659/4,976,027
23.7 (19.5–28.0)
293/1,726,743
17.3 (12.5–22.2)
  ≥ 5 days per week
164/1,300,269
20.2 (12.7–27.8)
115/633,191
14.8 (7.9–21.7)
Work hours
 
 
 
 
  ≤ 40 hours per week
666/4,555,070
22.5 (18.6–26.5)
819/4,514,730
17.3 (13.9–20.7)
  > 40 hours per week
1,193/8,597,108
24.9 (21.8–28.0)
735/4,309,882
17.3 (14.3–20.4)
Work schedule pattern
 
 
 
 
  Day working
1,526/10,805,797
24.5 (21.9–271)
1,312/7,305,852
18.3 (15.4–21.2)
  Non–day working
328/2,319,154
22.0 (16.6–27.4)
238/1,501,207
12.4 (6.8–18.1)
BMI category
 
 
 
 
  Underweight
40/272,239
0.0 (0.0–0.0)
85/539,963
0.0 (0.0–0.0)
  Normal
1,099/7,673,502
12.9 (10.3–15.4)
1,053/6,039,293
9.4 (7.5–11.4)
  Overweight
654/4,672,170
39.1 (34.3–43.9)
350/1,858,859
41.9 (35.7–48.1)
  Obese 61/500,005 68.3 (54.1–82.5) 65/384,483 46.1 (32.3–59.9)
*Subject number/estimated population number. Subject number varies due to item which was not answered. Unadjusted prevalence of the metabolic syndrome (95% confidence intervals).
Unadjusted and age-adjusted prevalence estimates for each occupational group stratified by gender are presented in Table 4. In the male workers, the overall unadjusted and age-adjusted prevalence estimates of the metabolic syndrome were 24.1% (95% CI: 21.7-26.5%) and 23.2% (95% CI: 21.0-25.5%), respectively. The prevalence estimates in male non-manual workers were 26.3% (95% CI: 22.3-30.2%) and 26.4% (95% CI: 22.3-30.5%), respectively, after age adjustment, which were the highest among the three occupational groups. In the occupational subgroups, “equipment, machine operation and assembling” workers showed the highest unadjusted prevalence of the metabolic syndrome (35.4%, 95% CI: 28.4-42.4%), followed by “managers” (31.7%, 95% CI: 18.1-45.3%) and “clerks” (26.9%, 95% CI: 21.0-32.8%). The highest age-adjusted prevalence for male workers was found in “professional and related” workers (27.3%, 95% CI: 20.9-33.6%), followed by “equipment, machine operation and assembling” workers (26.5%, 95% CI: 21.1-32.0%) and “managers” (26.5%, 95% CI: 14.2-38.8%).
Table 4
Unadjusted and age-adjusted prevalence of the metabolic syndrome by category of the Korean Standard Classification of Occupations stratified by gender
 
 
Prevalence of the metabolic syndrome
(95% confidence intervals)
Occupational groups Number * Unadjusted Age-adjusted
Overall male workers
1,859/13,152,179
24.1 (21.7–26.5)
23.2 (21.0–25.5)
Non-manual workers
676/4,905,005
26.3 (22.3–30.2)
26.4 (22.3–30.5)
  Managers
61/362,106
31.7 (18.1–45.3)
26.5 (14.2–38.8)
  Professional and related workers
335/2,531,917
25.0 (19.3–30.8)
27.3 (20.9–33.6)
  Clerks
280/2,010,981
26.9 (21.0–32.8)
24.6 (18.1–31.1)
Service/sales workers
304/2,302,276
19.9 (14.6–25.2)
21.5 (15.9–27.1)
  Service workers
104/910,156
15.7 (8.1–23.3)
17.5 (9.0–26.0)
  Sales workers
200/1,392,120
22.7 (15.3–30.0)
23.0 (16.2–29.8)
Manual workers
879/5,944,897
23.9 (20.6–27.1)
20.1 (17.3–23.0)
  Skilled agricultural, forestry and fishery workers
272/1,589,656
24.3 (18.2–30.4)
15.6 (10.9–20.2)
  Craft and related trades workers
206/1,733,288
15.7 (10.6–20.7)
16.4 (11.0–21.9)
  Equipment, machine operating and assembling workers
240/1,597,780
35.4 (28.4–42.4)
26.5 (21.1–32.0)
  Elementary workers
161/1,024,171
19.2 (11.3–27.2)
16.9 (9.4–24.4)
Overall female workers
1,544/8,824,612
17.3 (14.8–19.8)
19.5 (17.3–21.6)
Non-manual workers
545/3,325,220
7.7 (4.4–10.9)
20.8 (11.3–30.2)
  Managers
8/22,859
12.8 (−9.1–34.8)
10.6 (−6.7–27.9)
  Professional and related workers
334/1,998,628
7.3 (3.5–11.2)
27.9 (21.5–34.3)
  Clerks
203/1,303,732
8.1 (2.6–13.5)
9.8 (2.7–16.9)
Service/sales workers
428/2,502,853
16.9 (12.8–20.9)
18.4 (13–22.9)
  Service workers
215/1,340,314
16.9 (11.4–22.3)
20.5 (14.5–26.6)
  Sales workers
213/1,162,539
16.9 (11.2–22.5)
17.6 (11.9–23.2)
Manual workers
581/2,996,538
28.4 (23.9–32.9)
20.8 (16.9–24.7)
  Skilled agricultural, forestry and fishery workers
225/1,011,474
39.2 (31.8–46.6)
22.0 (15.2–28.9)
  Craft and related trades workers
42/258,235
19.1 (4.4–33.8)
12.0 (2.8–21.2)
  Equipment, machine operating and assembling workers
35/158,745
7.8 (−2.5–18.1)
6.2 (−1.7–14.2)
  Elementary workers 279/1,568,083 25.0 (19.1–31.0) 20.0 (14.5–25.5)
*Subject number/estimated population number. The prevalence estimate for each occupational group was above the upper bound of the 95% confidence interval for the overall prevalence estimate.
In the female workers, the estimates of overall unadjusted and age-adjusted prevalence of the metabolic syndrome were 17.3% (95% CI: 14.8-19.8%) and 19.5% (95% CI: 17.3-21.6%), respectively. Among the female workers, the age-adjusted prevalence of the metabolic syndrome was similar in both non-manual (20.8%, 95% CI: 11.3-30.2%) and manual (20.8%, 95% CI: 16.9-24.7%) workers, while the unadjusted prevalence was highest in manual workers (28.4%, 95% CI: 23.9-32.9%) and was lowest in non-manual workers (7.7%, 95% CI: 4.4-10.9%). In the individual occupational groups, the highest unadjusted prevalence was documented in “skilled agricultural, forestry and fishery” workers (39.2%, 95% CI: 31.8-46.6%), followed by “elementary” workers (25.0%, 95% CI: 19.1-31.0%) and “craft and related trades” workers (19.1%, 95% CI: 4.4-33.8%). “Professional and related” workers showed the highest age-adjusted prevalence of the metabolic syndrome among the female workers (27.9%, 95% CI: 21.5-34.3%), followed by “skilled agricultural, forestry and fishery” workers (22.0%, 95% CI: 15.2-28.9).
Table 5 shows the age-adjusted prevalence of the individual components of the metabolic syndrome by occupational group. Among the three occupational groups of non-manual, service/sales, and manual workers, the non-manual workers had the highest prevalence of high blood pressure (40.1%), hypertriglyceridemia (39.4%), low HDL-cholesterol level (20.5%), and hyperglycemia (31.8%) among the male workers. The highest prevalence of abdominal obesity was found in the service/sales workers among the male workers (28.6%). In the occupational subgroups, the prevalence estimate of abdominal obesity for male workers was highest in the “managers” (35.4%), followed by “craft and related trades” workers (31.1%) and “equipment, machine operation and assembling” workers (31.1%). “Clerks” also showed the highest prevalence of high blood pressure (51.6%) and hyperglycemia (34.5%) for male workers. Among the male workers, the highest prevalence of hypertriglyceridemia was found in the “equipment, machine operation and assembling” workers (44.9%), and the highest prevalence of low HDL-cholesterol levels was identified in the “professional and related” workers (22.0%), followed by “equipment, machine operation and assembling” workers (19.5%). Unlike the male workers, the prevalence of abdominal obesity among the female workers was highest in the “skilled agricultural, forestry and fishery” workers (50.5%), followed by “service” workers (42.0%), “professional and related” workers (41.8%), and “elementary” workers (40.9%). The highest prevalence of high blood pressure among the female workers was documented in the “craft and related trades” workers (32.3%). The highest prevalence of hypertriglyceridemia was found in the “managers” (31.8%). In the female workers, the “skilled agricultural, forestry and fishery” workers (43.0%) and “professional and related” workers (43.0%) showed the highest prevalence of low HDL-cholesterol levels. However, the prevalence of low HDL-cholesterol levels among male workers was lowest in the “skilled agricultural, forestry and fishery” workers (9.0%). The prevalence of hyperglycemia among the female workers was highest in the “professional and related” workers (24.7%).
Table 5
Age-adjusted prevalence of the components of the metabolic syndrome by category of the Korean Standard Classification of Occupations
 
Non-manual workers
Service/sales workers
Manual workers
 
Components Managers Professional and related workers Clerks Service workers Sales workers Skilled agricultural, forestry and fishery workers Craft and related trades workers Equipment, machine operation and assembling workers Elementary workers Total p-value
Male workers
 
 
 
 
 
 
 
 
 
 
 
  WC ≥ 90 cm (M)/80 cm (W)
 
24.5 (2.5)
 
28.6 (3.5)
 
24.0 (1.9)
 
25.1 (1.3)
0.946
35.4 (8.7)
21.1 (2.8)
25.7 (3.7)
25.7 (4.7)
28.2 (3.9)
22.8 (3.5)
31.1 (4.3)
31.0 (3.2)
18.2 (4.2)
0.705
  BP ≥ 130/85 mmHg or treated
 
40.1 (2.5)
 
33.3 (3.3)
 
32.7 (1.7)
 
36.3 (1.4)
0.036
46.0 (6.9)
33.2 (3.5)
51.6 (2.6)
29.8 (4.4)
35.5 (3.8)
26.6 (3.3)
29.0 (3.5)
32.7 (2.6)
36.2 (4.1)
<0.001
  TG ≥ 150 mg/dl
 
39.4 (2.6)
 
35.5 (2.7)
 
35.3 (2.2)
 
37.4 (1.4)
0.225
41.8 (8.0)
43.9 (3.3)
33.7 (3.8)
35.2 (5.0)
37.7 (3.3)
25.9 (4.6)
34.7 (4.0)
44.9 (2.9)
29.9 (4.9)
0.119
  HDL-C < 40 mg/dl
 
20.5 (2.2)
 
13.3 (2.5)
 
18.3 (1.8)
 
19.2 (1.2)
0.024
14.9 (4.1)
22.0 (3.2)
16.9 (2.5)
12.6 (3.8)
13.5 (3.0)
9.0 (1.5)
17.1 (3.0)
19.5 (2.9)
18.8 (4.6)
0.119
  FPG ≥ 100 mg/dl or treated
 
31.8 (2.5)
 
29.3 (3.4)
 
26.2 (1.7)
 
28.6 (1.3)
0.191
31.2 (7.6)
31.8 (3.2)
34.5 (4.1)
26.2 (5.1)
29.2 (3.8)
20.3 (2.4)
25.8 (3.5)
27.1 (2.8)
26.8 (3.4)
0.284
Female workers
 
 
 
 
 
 
 
 
 
 
  WC ≥ 90 cm (M)/80 cm (W)
 
34.6 (4.8)
 
39.0 (2.5)
 
41.8 (3.3)
 
36.8 (1.4)
<0.001
19.5 (12.2)
41.8 (3.4)
24.6 (4.3)
42.0 (3.4)
36.9 (3.2)
50.5 (6.7)
32.0 (5.1)
22.4 (5.4)
40.9 (5.0)
<0.001
  BP ≥ 130/85 mmHg or treated
 
21.0 (1.8)
 
23.8 (2.2)
 
27.6 (1.9)
 
25.6 (1.2)
<0.001
29.4 (10.8)
19.0 (2.2)
23.2 (3.3)
26.4 (2.9)
21.3 (3.0)
29.0 (4.2)
32.3 (4.8)
7.1 (4.0)
27.0 (2.5)
<0.001
  TG ≥ 150 mg/dl
 
15.7 (2.7)
 
23.3 (2.9)
 
17.6 (2.1)
 
17.9 (1.1)
<0.001
31.8 (13.2)
18.4 (2.1)
5.6 (2.0)
22.7 (4.5)
23.6 (3.4)
16.1 (2.6)
9.5 (4.0)
8.3 (4.8)
18.4 (2.8)
<0.001
  HDL-C < 50 mg/dl
 
34.9 (4.7)
 
32.2 (2.9)
 
34.7 (3.1)
 
32.8 (1.4)
<0.001
15.1 (10.8)
43.0 (2.6)
21.2 (4.3)
33.2 (3.6)
33.0 (4.0)
43.0 (5.8)
37.9 (8.4)
16.8 (5.1)
32.1 (5.1)
<0.001
  FPG ≥ 100 mg/dl or treated  
19.8 (4.5)
 
16.1 (1.9)
 
19.0 (2.0)
 
18.1 (1.1) <0.001
9.4 (8.6) 24.7 (3.7) 15.6 (3.5) 15.3 (3.1) 17.1 (2.8) 14.9 (1.8) 9.0 (2.2) 15.2 (5.8) 20.7 (2.5) <0.001
Abbreviation: All values were the estimated percentage (standard error). WC waist circumference, BP blood pressure, TG triglyceride, HDL-C high-density lipoprotein cholesterol, FPG fasting plasma glucose, M male, F female.
Table 6 shows the results of multiple logistic regression analyses. Manual workers were significantly less likely to have the metabolic syndrome (odds ratio: 0.62, 95% CI: 1.19-5.86) relative to non-manual workers among male workers after adjustment for age, level of education, household income, high risk drinking, smoking status, and vigorous physical activity (Model I). After additional adjustment for work hours and work schedule pattern, both manual (0.63, 95% CI: 0.39-0.99) and service/sales (0.59, 95% CI: 0.41-0.85) workers had significantly lower odds of having the metabolic syndrome compared to non-manual workers among the male workers (Model II). There were no significant associations between the metabolic syndrome and the occupational group among female workers in either model. When comparing the subgroups of service/sales and manual workers with the non-manual workers as a reference, “service” workers, “craft and related trades” workers, and “elementary” workers showed significantly lower odds among the male workers.
Table 6
Multiple logistic regression to assess the relationship between occupation and meeting criteria for the metabolic syndrome among Korean workers aged ≥20 years
 
Odds ratio (95% confidence intervals)
  Male Female
Model I*
 
 
Occupational group
 
 
 Non-manual workers
1.00 (reference)
1.00 (reference)
  Service/sales workers
0.66 (0.42–1.02)
0.98 (0.45–2.12)
  Service workers
0.49 (0.25–0.96)
0.92 (0.36–2.32)
  Sales workers
0.74 (0.43–1.28)
1.12 (0.51–2.46)
 Manual workers
0.62 (0.44–0.88)
1.00 (0.46–2.16)
  Skilled agricultural, forestry and fishery workers
0.38 (0.20–0.70)
1.56 (0.56–4.33)
  Craft and related trades workers
0.39 (0.23–0.66)
0.78 (0.21–2.83)
  Equipment, machine operating and assembling workers
1.22 (0.82–1.83)
0.88 (0.16–4.67)
  Elementary workers
0.43 (0.21–0.91)
0.84 (0.38–1.86)
Model II
 
 
Occupational groups
 
 
 Non-manual workers
1.00 (reference)
1.00 (reference)
  Service/sales workers
0.63 (0.39–0.99)
1.04 (0.48–2.25)
  Service workers
0.45 (0.22–0.93)
0.98 (0.39–2.47)
  Sales workers
0.73 (0.42–1.26)
1.16 (0.53–2.57)
 Manual workers
0.59 (0.41–0.85)
1.02 (0.47–2.21)
  Skilled agricultural, forestry and fishery workers
0.37 (0.20–0.69)
1.54 (0.56–4.25)
  Craft and related trades workers
0.37 (0.22–0.63)
0.78 (0.22–2.81)
  Equipment, machine operating and assembling workers
1.16 (0.77–1.75)
0.90 (0.17–4.87)
  Elementary workers 0.42 (0.19–0.91) 0.87 (0.39–1.94)
* Model I: Adjusted for age, level of education, household income, high-risk drinking, smoking status, and vigorous physical activity.
Model II: Adjusted for Model I factors, plus work hours, and work schedule.
In this study, we assessed the prevalence of the metabolic syndrome by occupational group among Korean workers and evaluated the risk of the metabolic syndrome among each of the occupational groups. Our study demonstrates variability in the prevalence of the metabolic syndrome by occupational group, and found the greatest risk for the metabolic syndrome in male non-manual workers.
Several studies have identified differences in the prevalence of the metabolic syndrome by occupational group [8-10]. In Spanish workers, the presence of the metabolic syndrome after age adjustment was greatest in the “machine installers, operators, and assemblers” (15.1%) group among males, with an overall prevalence of 9.5% (11.6% in male workers and 4.1% in female workers). Manual workers had a higher prevalence than non-manual workers in both males and females [8]. According to a study of the U.S. working population, the overall prevalence of the metabolic syndrome was 20.6% (20.2% in male workers and 21.4% in female workers) with the greatest unadjusted prevalence among “transportation and material occupations” (33.1%) and the greatest age-adjusted prevalence among “food preparation and food service workers” (31.1%) [9]. In a study using the KNHANES (2005) data, the prevalence of the metabolic syndrome among Korean workers was found to be 21.8% (22.5% in male worker and 15.9% in female), and the prevalence was higher in manual workers than in non-manual workers [10].
In this study, non-manual workers showed higher unadjusted and age-adjusted prevalences of the metabolic syndrome than service/sales and manual workers among the male workers. Most of the workers in the non-manual groups spend most of their work hours sedentary [15]. Furthermore, they may also engage in less physical activity relative to other workers. Actually, the proportion of those engaging in vigorous physical activity at least 5 days a week in these groups was lower than in the other workers in this study.
In the male non-manual group, the “managers” showed the highest prevalence estimate (31.7%), but the prevalence in the “equipment, machine operating and assembling” workers was the highest (35.4%) among the nine occupational subgroups before age adjustment. On the other hand, after age adjustment, the highest prevalence was observed in “professional and related” workers (27.3%), followed by “managers” (26.5%) and “equipment, machine operating and assembling” workers (26.5%). The subgroups of non-manual workers including “managers”, “professional and related” workers, and “clerks” had a higher level of education and household income than the manual working groups in both the male and female workers. Several studies have shown an inverse association between socioeconomic status and the metabolic syndrome in women, but no association in men [16-18]. However, a recent study of the Korean population using 2007–2008 KNHANES data has reported that socioeconomic status (SES) had a positive association with the metabolic syndrome for men and an inverse association for women [19]. The researchers suggested differences in health behaviors including smoking and drinking, food consumption, heath care assessment, and psychological stress according to SES as possible explanations for the inverse association in women. The authors explained that the finding of high prevalence of metabolic syndrome in men with highest household income was consistent with an earlier study using data from the 1998 to 2001 KNHANES, which showed a positive relationship between obesity and higher SES in men [20]. This positive association among men might be applied to explain the data on the male workers in our study. The subgroups of non-manual male workers including “managers”, “professional and related” workers, and “clerks” had a higher proportion of overweight and obese individuals than the other occupational groups in our study.
Among the subgroups of male manual workers, only “equipment, machine operating and assembling” workers showed a significantly higher prevalence of the metabolic syndrome than the prevalence for the male workers overall before and after age adjustment, and the prevalence was similar to the prevalence in non-manual workers. This observation was in concordance with a previous study in Spain, which showed the highest prevalence of the metabolic syndrome in the “machine installers, operators and assemblers” group among all of the occupational groups [8]. When the demographic characteristics of this group were considered, they were found to have a higher level of education (high school education and more) and household income (middle to high) in the manual worker groups. It seems that higher socioeconomic status, among other factors, might have influenced this result.
Among the female workers, although the unadjusted prevalence was greatest in the manual workers (28.4%) and lowest in the non-manual workers (7.3%), this difference disappeared after age standardization (20.8% versus 20.8%, respectively). Among the subgroups of the female non-manual workers, “professional and related” workers showed the lowest unadjusted prevalence of the metabolic syndrome (7.3%) and the highest age-adjusted prevalence (27.9%). This was the main cause for the increase in the overall prevalence in non-manual workers after age adjustment. Although not presented in this paper, the age distribution of female “professional and related” workers was skewed toward younger ages. At this age group, the prevalence of the metabolic syndrome was lower, but compared to the younger group, the prevalence in the older age group was extremely high. In the multiple logistic regression analysis, there was no significant association found between occupational groups and the metabolic syndrome in female workers.
Unlike the prevalence estimate of the male “skilled agricultural, forestry and fishery” workers, which was significantly lower than the overall male prevalence after age adjustment, female workers of the same occupational group continued to show significantly higher prevalence of the metabolic syndrome compared to the overall prevalence after age adjustment. This distinct feature was also evident in the analysis of individual components of the metabolic syndrome. Female “skilled agricultural, forestry and fishery” workers presented the highest age-adjusted prevalence of abdominal obesity and low HDL-cholesterol levels among the occupational subgroups. Conversely, male “skilled agricultural, forestry and fishery” workers showed the lowest age-adjusted prevalence of low HDL-cholesterol levels and a relatively lower prevalence of abdominal obesity. These gender differences may come from post-menopausal hormonal changes in female workers, given that recent studies have shown that the prevalence of the metabolic syndrome was higher in postmenopausal women than in premenopausal women [21-24]. In the present study, “skilled agricultural, forestry and fishery” workers were the most aged group; that is, more female workers of that group could be expected to be post-menopausal based on their age than in the other groups.
We categorized service and sales workers into a separate group, apart from the non-manual and manual workers. Our results showed that service/sales workers had characteristics intermediate to the other two occupational groups with regard to SES. Likewise, the age-adjusted prevalence of the metabolic syndrome among the male service/sales workers was between the prevalence in non-manual workers and the prevalence in manual workers. In the women also, considering that the dramatic increase of the prevalence in non-manual workers after age adjustment was mainly due to the uneven distribution of age, the prevalence of the metabolic syndrome in service/sales workers stood between those of manual and non-manual workers.
In this study, the work schedule pattern was included as a covariate. In both male and female workers, the percentages of night/overnight or shift work were the highest for the service workers. Generally, it is known that shift work causes the disturbance of sleep and normal circadian rhythms, and it may increase psychosocial stress, predisposing the worker to physiological disturbances related to the metabolic syndrome and cardiovascular disease [25,26]. Recent studies have shown that shift work is closely related to the increased risk of the metabolic syndrome [27-31]. However, the prevalence of the metabolic syndrome in this group was not higher compared to the other occupational groups. In addition, the result of multiple logistic regression analysis did not show a significant association between the metabolic syndrome and work schedule (data not shown).
The strengths of our investigation are the use of a large sample representative of the Korean population and the analysis of the prevalence of the metabolic syndrome in 9 occupational groups considering multiple variables such as age, gender, level of education, household income, and smoking status. The limitations are an inability to draw causal inferences due to the cross-sectional design and unavailability of detailed information about work-related condition in the KNHANES.
In conclusion, our study demonstrated variability in the prevalence of the metabolic syndrome by occupational group among Korean workers. In the male workers, non-manual workers appeared to be more vulnerable to the metabolic syndrome compared to service/sales workers or manual workers, but not in the female workers. Future research should evaluate factors that may influence the occurrence of the metabolic syndrome in each occupational group so that our findings can be utilized to establish appropriate preventive measures for the metabolic syndrome and co-occurring diseases including cardiovascular disease and diabetes.
The authors declare that they have no competing interests.
DH Kim and JY Ryu designed the research. S Hong and CH Kim collected the data. JY Ryu and S Lee performed the statistical analysis. JY Ryu, JT Lee, JH Kim, and DH Kim interpreted the data. JY Ryu and S Lee wrote the manuscript. All of the authors read and approved the final manuscript.
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Figure & Data

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    Prevalence of the Metabolic Syndrome among Korean Workers by Occupational Group: Fifth Korean National Health and Nutrition Examination Survey (KNHANES) 2010
    Prevalence of the Metabolic Syndrome among Korean Workers by Occupational Group: Fifth Korean National Health and Nutrition Examination Survey (KNHANES) 2010
     ManagersProfessional and related workersClerksService workersSales workersSkilled agricultural, forestry and fishery workersCraft and related trades workersEquipment, machine operation and assembling workersElementary workersTotalp-value
    Age (years)*
    50.9 (1.3)
    38.2 (0.7)
    39.1(0.7)
    36.8 (1.4)
    41.2 (1.2)
    56.4 (1.4)
    42.7 (0.9)
    45.1 (1.1)
    46.1 (1.7)
    44.1 (0.4)
    < 0.001
    Education
     
     
     
     
     
     
     
     
     
     
    < 0.001
      ≤ Elementary school
    0.0 (0.0)
    0.6 (0.4)
    0.4 (0.4)
    4.9 (2.1)
    6.5 (2.1)
    41.5 (3.3)
    14.2 (2.7)
    7.7 (1.8)
    21.7 (4.3)
    10.7 (1.1)
     
      Middle school
    16.3 (5.6)
    0.4 (0.3)
    1.7 (1.0)
    6.4 (2.4)
    7.6 (2.2)
    20.8 (3.9)
    13.9 (2.5)
    19.7 (3.0)
    17.5 (3.6)
    10.3 (0.9)
     
      High school
    31.8 (6.7)
    21.0 (3.6)
    27.6 (3.4)
    56.3 (5.4)
    45.7 (4.4)
    24.9 (3.2)
    53.3 (4.0)
    56.9 (4.0)
    50.5 (4.9)
    39.2 (1.5)
     
      ≥ University
    51.8 (6.7)
    78.0 (3.6)
    70.3 (3.6)
    32.4 (4.8)
    40.2 (3.9)
    12.8 (2.8)
    18.6 (3.0)
    15.7 (3.2)
    10.3 (2.8)
    39.8 (1.7)
     
    Household income
     
     
     
     
     
     
     
     
     
     
    < 0.001
      Low
    3.7 (2.7)
    6.7 (1.8)
    2.7 (1.1)
    6.5 (2.7)
    9.3 (2.2)
    24.1 (4.0)
    12.3 (2.8)
    8.6 (2.4)
    26.5 (4.2)
    10.9 (1.0)
     
      Low-middle
    10.6 (4.4)
    17.1 (2.7)
    24.5 (2.8)
    34.6 (2.7)
    27.6 (3.6)
    28.2 (4.3)
    35.4 (3.7)
    26.9 (3.5)
    29.2 (4.3)
    26.4 (1.4)
     
      Middle-high
    29.2 (7.2)
    39.0 (3.0)
    33.9 (3.1)
    25.0 (4.4)
    36.1 (4.3)
    18.2 (2.6)
    29.0 (3.4)
    37.6 (3.6)
    29.5 (4.9)
    31.9 (1.4)
     
      High
    56.5 (6.1)
    37.3 (2.9)
    38.9 (3.7)
    33.9 (5.2)
    27.0 (3.7)
    29.5 (4.2)
    23.4 (3.3)
    26.9 (3.4)
    14.8 (3.6)
    30.7 (1.6)
     
    High-risk drinking
     
     
     
     
     
     
     
     
     
     
    0.002
      Never
    17.5 (5.2)
    12.7 (2.1)
    14.1 (2.3)
    7.4 (2.6)
    13.0 (2.7)
    18.1 (3.6)
    14.1 (2.5)
    14.8 (2.3)
    26.4 (4.6)
    14.8 (1.0)
     
      Once a month
    13.4 (6.3)
    46.3 (3.4)
    38.9 (3.3)
    44.4 (5.8)
    33.7 (4.0)
    32.6 (4.3)
    42.5 (4.5)
    39.2 (4.3)
    35.9 (5.5)
    40.0 (1.5)
     
      Once a weak
    30.0 (6.6)
    30.2 (3.2)
    38.3 (3.6)
    35.5 (5.3)
    43.6 (4.3)
    26.2 (4.1)
    28.8 (3.8)
    29.7 (3.5)
    20.2 (4.7)
    31.8 (1.2)
     
      Everyday
    9.1 (4.2)
    10.7 (2.0)
    8.7 (2.2)
    12.7 (3.6)
    9.8 (2.6)
    23.2 (3.3)
    14.6 (2.7)
    16.3 (3.2)
    17.5 (4.0)
    13.4 (1.1)
     
    Smoking status
     
     
     
     
     
     
     
     
     
     
    0.027
      Non-smoker
    15.0 (4.4)
    23.7 (2.4)
    17.7 (2.6)
    18.7 (3.9)
    17.9 (3.1)
    13.9 (2.8)
    12.0 (2.4)
    10.9 (2.5)
    15.5 (3.9)
    16.5 (1.0)
     
      Ex-smoker
    41.1 (6.1)
    30.1 (2.9)
    31.6 (2.8)
    23.9 (4.4)
    31.8 (3.7)
    41.8 (3.0)
    32.7 (3.6)
    34.4 (3.1)
    29.5 (4.3)
    32.6 (1.3)
     
      Current smoker
    43.9 (6.0)
    46.3 (3.4)
    50.8 (2.9)
    57.4 (5.1)
    50.3 (4.4)
    44.3 (3.5)
    55.4 (3.7)
    54.7 (3.4)
    55.0 (5.3)
    50.9 (1.4)
     
    Vigorous physical activity
     
     
     
     
     
     
     
     
     
     
    < 0.001
      None
    66.2 (6.4)
    53.3 (3.8)
    44.4 (3.6)
    52.1 (5.1)
    50.2 (3.5)
    60.7 (3.3)
    53.3 (4.2)
    49.4 (3.7)
    58.8 (5.2)
    52.7 (1.4)
     
      < 5 days per week
    30.3 (6.1)
    42.8 (3.9)
    49.7 (3.6)
    35.7 (5.2)
    37.1 (4.1)
    21.8 (2.8)
    36.1 (4.1)
    41.4 (3.7)
    26.4 (5.2)
    37.6 (1.4)
     
      ≥ 5 days per week
    3.5 (2.1)
    3.8 (1.2)
    5.8 (1.4)
    12.3 (3.6)
    12.7 (3.0)
    17.5 (2.6)
    10.7 (2.2)
    9.2 (2.4)
    14.8 (4.1)
    9.7(0.8)
     
    Work hours
     
     
     
     
     
     
     
     
     
     
    < 0.001
      ≤ 40 hours per week
    48.8 (6.5)
    41.0 (3.6)
    42.6 (3.3)
    28.5 (4.7)
    28.3 (3.9)
    37.8 (4.4)
    25.6 (2.9)
    23.6 (3.2)
    39.4 (4.8)
    34.4 (1.3)
     
      > 40 hours per week
    51.2 (6.5)
    59.0 (3.6)
    57.4 (3.3)
    71.5 (4.7)
    71.7 (3.9)
    62.2 (4.4)
    74.4 (2.9)
    76.4 (3.2)
    60.6 (4.8)
    65.6 (1.3)
     
    Work schedule pattern
     
     
     
     
     
     
     
     
     
     
    < 0.001
      Day
    92.0 (4.5)
    81.7 (2.5)
    90.9 (2.2)
    48.6 (5.7)
    84.8 (3.0)
    99.8 (0.2)
    87.2 (3.5)
    72.9 (3.3)
    68.5 (4.1)
    82.2 (1.2)
     
      Night/overnight
    3.7 (2.0)
    13.6 (2.3)
    2.6 (1.1)
    26.3 (5.3)
    14.2 (3.0)
    0.1 (0.1)
    2.0 (1.3)
    8.7 (2.0)
    11.3 (2.8)
    8.6 (0.8)
     
      Shift
    0.0
    1.5 (0.9)
    5.2 (1.9)
    15.5 (4.1)
    0.3 (0.2)
    0.0
    8.4 (2.7)
    11.3 (2.5)
    19.4 (3.2)
    6.3 (0.8)
     
      Others
    4.2 (4.1)
    3.2 (1.0)
    1.3 (0.7)
    9.6 (2.7)
    0.7 (0.5)
    0.1 (0.1)
    2.4 (2.0)
    7.1 (2.2)
    0.8 (0.7)
    2.9 (0.5)
     
    BMI category
     
     
     
     
     
     
     
     
     
     
    0.230
      Normal/underweight
    55.2 (7.6)
    56.6 (3.0)
    58.1 (3.5)
    60.5 (5.8)
    62.8 (4.2)
    68.5 (3.5)
    61.4 (3.3)
    62.2 (3.7)
    67.0 (4.5)
    61.3 (1.4)
     
      Overweight
    37.5 (6.4)
    39.3 (2.9)
    36.4 (3.6)
    37.7 (5.7)
    30.5 (3.7)
    30.8 (3.4)
    35.2 (3.2)
    33.5 (3.6)
    30.1 (4.5)
    34.7 (1.3)
     
      Obese7.3 (3.7)4.1 (1.3)5.5 (1.7)1.8 (1.3)6.7 (2.0)0.7 (0.5)3.4 (1.5)4.3 (1.5)2.9 (1.4)3.9 (0.6) 
     ManagersProfessional and related workersClerksService workersSales workersSkilled agricultural, forestry and fishery workersCraft and related trades workersEquipment, machine operation and assembling workersElementary workersTotalp-value
    Age (yr)*
    54.1 (3.9)
    34.2 (0.6)
    33.7 (0.7)
    43.2 (1.0)
    43.2 (1.0)
    57.4 (1.5)
    49.1 (2.9)
    41.8 (2.4)
    51.7 (1.0)
    45.4 (0.6)
    < 0.001
    Education
     
     
     
     
     
     
     
     
     
     
    < 0.001
      ≤ Elementary school
    0.0 (0.0)
    0.6 (0.3)
    0.3 (0.3)
    21.7 (3.3)
    18.4 (2.6)
    67.2 (4.7)
    30.4 (9.7)
    16.5 (7.4)
    39.8 (3.0)
    22.3 (1.9)
     
      Middle school
    18.2 (15.1)
    0.6 (0.4)
    2.2 (1.0)
    18.3 (2.9)
    13.3 (2.5)
    15.5 (4.5)
    34.5 (8.4)
    17.2 (7.6)
    18.5 (3.4)
    11.6 (1.1)
     
      High school
    18.4 (12.9)
    17.1 (2.5)
    50.1 (3.9)
    47.3 (3.6)
    47.6 (3.7)
    15.0 (4.2)
    31.8 (7.6)
    60.4 (10.3)
    34.7 (3.7)
    34.5 (1.7)
     
      ≥ University
    63.3 (18.0)
    81.7 (2.5)
    47.4 (4.1)
    12.6 (2.7)
    20.7 (3.0)
    2.3 (1.4)
    3.3 (2.3)
    5.8 (4.1)
    6.9 (1.8)
    31.5 (1.8)
     
    Household income
     
     
     
     
     
     
     
     
     
     
    < 0.001
      Low
    0.0 (0.0)
    4.0 (1.4)
    2.6 (1.2)
    10.0 (2.3)
    12.1 (2.3)
    35.7 (4.9)
    30.6 (9.4)
    0.0 (0.0)
    25.1 (2.9)
    14.2 (1.3)
     
      Low-middle
    1.2 (1.2)
    17.2 (2.7)
    20.7 (3.8)
    31.1 (3.6)
    23.0 (3.8)
    25.6 (3.2)
    23.6 (6.1)
    23.9 (7.7)
    36.9 (3.4)
    25.4 (1.5)
     
      Middle-high
    14.6 (13.3)
    37.4 (3.3)
    36.8 (4.2)
    30.7 (3.8)
    35.4 (3.8)
    18.0 (3.3)
    28.2 (7.6)
    45.2 (10.9)
    22.6 (2.5)
    30.8 (1.5)
     
      High
    84.2 (13.4)
    41.4 (3.4)
    40.0 (3.8)
    28.2 (3.3)
    29.6 (3.7)
    20.7 (3.2)
    17.6 (6.5)
    30.9 (9.5)
    15.4 (2.6)
    29.6 (1.6)
     
    High-risk drinking
     
     
     
     
     
     
     
     
     
     
    < 0.001
      Never
    77.4 (15.6)
    39.6 (3.5)
    31.7 (3.9)
    35.9 (3.9)
    43.6 (3.8)
    57.0 (5.4)
    18.5 (6.7)
    37.1 (11.3)
    42.7 (5.0)
    39.8 (1.7)
     
      Once a month
    22.6 (15.6)
    45.0 (3.7)
    52.9 (4.3)
    43.5 (4.0)
    37.8 (4.2)
    38.4 (4.4)
    58.6 (9.3)
    59.8 (11.7)
    35.9 (3.9)
    43.6 (4.6)
     
      Once a weak
    0.0 (0.0)
    15.4 (3.2)
    14.7 (3.0)
    13.6 (2.6)
    17.2 (3.3)
    4.0 (2.2)
    19.5 (8.5)
    3.1 (3.1)
    14.3 (3.3)
    13.8 (1.3)
     
      Everyday
    0.0 (0.0)
    0.0 (0.0)
    0.7 (0.7)
    7.0 (2.0)
    1.3 (1.3)
    0.6 (0.6)
    3.4 (2.6)
    0.0 (0.0)
    7.1 (3.0)
    2.7 (0.6)
     
    Smoking status
     
     
     
     
     
     
     
     
     
     
    0.015
      Non-smoker
    100.0 (0.0)
    88.5 (1.9)
    86.3 (2.7)
    86.0 (3.1)
    83.4 (3.0)
    96.4 (1.7)
    91.8 (5.6)
    96.7 (3.3)
    83.0 (3.2)
    87.4 (1.2)
     
      Ex-smoker
    0.0 (0.0)
    7.5 (1.6)
    7.9 (2.2)
    4.9 (1.7)
    9.5 (2.4)
    2.3 (1.4)
    8.0 (5.6)
    0.0 (0.0)
    5.4 (1.7)
    6.3 (0.8)
     
      Current smoker
    0.0 (0.0)
    4.0 (1.1)
    5.8 (1.8)
    9.2 (2.9)
    7.1 (2.2)
    1.3 (0.8)
    0.1 (0.1)
    3.3 (3.3)
    11.6 (3.1)
    6.3 (0.9)
     
    Vigorous physical  activity
     
     
     
     
     
     
     
     
     
     
    0.007
      None
    55.8 (18.7)
    74.1 (3.1)
    70.2 (3.7)
    70.1 (3.7)
    69.5 (3.8)
    76.1 (4.1)
    86.3 (5.4)
    61.5 (8.8)
    75.0 (3.2)
    72.9 (1.4)
     
      < 5 days per week
    44.2 (18.7)
    21.8 (2.9)
    26.2 (3.6)
    20.4 (3.6)
    23.7 (3.3)
    11.4 (2.7)
    6.5 (3.6)
    23.9 (8.4)
    16.2 (2.4)
    19.8 (1.2)
     
      ≥ 5 days per week
    0.0 (0.0)
    4.1 (1.3)
    3.6 (1.4)
    9.5 (2.3)
    6.8 (2.0)
    12.5 (3.3)
    7.2 (4.3)
    14.6 (5.6)
    8.8 (2.0)
    7.3 (0.8)
     
    Work hours
     
     
     
     
     
     
     
     
     
     
    < 0.001
      ≤ 40 hours per week
    80.4 (13.9)
    57.0 (3.5)
    52.4 (4.2)
    33.7 (4.0)
    48.9 (4.0)
    50.9 (4.0)
    29.4 (7.3)
    35.9 (9.9)
    64.5 (3.6)
    51.2 (1.6)
     
      > 40 hours per week
    19.6 (13.9)
    43.0 (3.5)
    47.6 (4.2)
    66.3 (4.0)
    51.1 (4.0)
    49.1 (4.0)
    70.6 (7.3)
    64.1 (9.9)
    35.5 (3.6)
    48.8 (1.6)
     
    Work schedule pattern
     
     
     
     
     
     
     
     
     
     
    <0.001
      Day
    93.8 (5.4)
    74.8 (3.2)
    94.3 (2.0)
    70.2 (3.7)
    77.7 (3.4)
    99.0 (0.7)
    93.0 (4.6)
    74.2 (9.6)
    85.8 (2.7)
    82.7 (1.5)
     
      Night/overnight
    5.1 (5.1)
    18.9 (3.0)
    3.2 (1.5)
    24.5 (3.4)
    15.6 (2.9)
    0.0
    4.6 (2.6)
    6.1 (3.8)
    12.0 (2.6)
    12.9 (1.3)
     
      Shift
    1.1 (1.2)
    3.8 (1.5)
    1.7 (1.3)
    2.2 (0.9)
    3.7 (1.7)
    0.3 (0.3)
    2.4 (2.4)
    8.1 (6.1)
    1.2 (0.6)
    2.4 (0.5)
     
      Others
    0.0
    2.5 (1.0)
    0.7 (0.5)
    3.1 (1.2)
    3.0 (1.4)
    0.7 (0.6)
    0.0
    11.6 (9.0)
    1.0 (0.5)
    2.0 (0.4)
     
    BMI category
     
     
     
     
     
     
     
     
     
     
    0.009
      Normal/underweight
    82.8 (11.7)
    82.9 (2.5)
    79.7 (3.2)
    72.2 (3.2)
    68.5 (4.0)
    66.8 (4.4)
    69.4 (8.0)
    70.3 (9.6)
    70.9 (2.6)
    74.2 (1.3)
     
      Overweight
    17.2 (11.7)
    14.5 (2.2)
    15.0 (2.6)
    22.5 (3.0)
    27.6 (4.0)
    26.4 (3.3)
    30.5 (8.0)
    17.3 (7.8)
    24.4 (2.7)
    21.2 (1.1)
     
      Obese0.0 (0.0)2.6 (1.2)5.2 (1.9)5.3 (1.8)3.9 (1.5)6.8 (1.9)0.1 (0.1)12.4 (7.0)4.7 (1.3)4.5 (0.7) 
     
    Male
    Female
    DemographicsNumber *† Prevalence (95% confidence intervals) Number *† Prevalence (95% confidence intervals)
    Age group
     
     
     
     
      20–29 years
    152/1,942,533
    9.2 (4.1–14.3)
    231/1,733,502
    3.5 (0.7–6.2)
      30–39 years
    428/3,276,013
    17.8 (13.5–22.1)
    291/1,634,571
    5.5 (2.0–9.0)
      40–49 years
    477/3,659,709
    25.9 (21.3–30.4)
    371/2,433,142
    12.5 (8.2–16.8)
      50–59 years
    392/2,681,787
    35.7 (30.2–41.2)
    374/1,891,022
    30.8 (25.2–36.5)
      60–69 years
    297/1,176,249
    36.4 (29.5–43.3)
    188/758,966
    38.0 (30.1–45.8)
      ≥ 70 years
    113/415,885
    17.4 (9.1–25.8)
    93/373,407
    53.5 (43.5–63.4)
    Education
     
     
     
     
      ≤ Elementary school
    262/1,377,314
    28.7 (21.5–35.8)
    407/1,912,522
    40.9 (35.6–46.2)
      Middle school
    218/1,385,292
    35.9 (29.0–42.8)
    175/989,224
    24.4 (16.6–32.3)
      High school
    637/5,078,713
    20.1 (16.4–23.7)
    491/3,089796
    9.3 (6.1–12.5)
      ≥ University
    742/5,310,859
    23.6 (19.9–27.4)
    481/2,833,069
    7.6 (4.2–11.1)
    Household income
     
     
     
     
      Low
    224/1,362,396
    25.9 (18.9–32.9)
    239/1,171,008
    35.3(28.6–41.9)
      Low–middle
    476/3,488,782
    21.4 (16.9–25.8)
    366/2,177,822
    19.8 (15.3–24.2)
      Middle–high
    568/4,173,072
    23.8 (19.4–28.2)
    448/2,712,764
    14.3 (10.7–18.0)
      High
    575/4,051,739
    25.5 (21.1–29.9)
    481/2,648,160
    10.4 (7.1–13.7)
    High–risk drinking
     
     
     
     
      Never
    275/1,681,687
    14.7 (9.6–19.9)
    473/2,633,998
    15.4 (11.2–19.7)
      Once a month
    644/4,713,082
    21.2 (17.4–24.9)
    494/2,956,125
    12.8 (9.3–16.4)
      Once a weak
    490/3,727,662
    26.0 (21.6–30.4)
    130/932,867
    17.4 (9.6–25.2)
      Everyday
    226/1,602,909
    38.1 (30.7–45.5)
    23/152,018
    31.1 (8.8–53.4)
    Smoking status
     
     
     
     
      Non–smoker
    320/2,194,133
    19.5 (14.4–24.5)
    1,394/7,721,944
    17.5 (14.9–20.2)
      Ex–smoker
    697/4,369,598
    27.0 (22.9–31.0)
    81/546,406
    16.0 (7.0–25.0)
      Current smoker
    841/6,585,245
    23.7 (20.1–27.3)
    78/547,078
    15.8 (6.7–24.9)
    Vigorous physical activity
     
     
     
     
      None
    1,035/6,872,680
    25.0 (21.9–28.1)
    1,144/6,444,936
    17.8 (14.4–20.7)
      < 5 days per week
    659/4,976,027
    23.7 (19.5–28.0)
    293/1,726,743
    17.3 (12.5–22.2)
      ≥ 5 days per week
    164/1,300,269
    20.2 (12.7–27.8)
    115/633,191
    14.8 (7.9–21.7)
    Work hours
     
     
     
     
      ≤ 40 hours per week
    666/4,555,070
    22.5 (18.6–26.5)
    819/4,514,730
    17.3 (13.9–20.7)
      > 40 hours per week
    1,193/8,597,108
    24.9 (21.8–28.0)
    735/4,309,882
    17.3 (14.3–20.4)
    Work schedule pattern
     
     
     
     
      Day working
    1,526/10,805,797
    24.5 (21.9–271)
    1,312/7,305,852
    18.3 (15.4–21.2)
      Non–day working
    328/2,319,154
    22.0 (16.6–27.4)
    238/1,501,207
    12.4 (6.8–18.1)
    BMI category
     
     
     
     
      Underweight
    40/272,239
    0.0 (0.0–0.0)
    85/539,963
    0.0 (0.0–0.0)
      Normal
    1,099/7,673,502
    12.9 (10.3–15.4)
    1,053/6,039,293
    9.4 (7.5–11.4)
      Overweight
    654/4,672,170
    39.1 (34.3–43.9)
    350/1,858,859
    41.9 (35.7–48.1)
      Obese61/500,00568.3 (54.1–82.5)65/384,48346.1 (32.3–59.9)
     
     
    Prevalence of the metabolic syndrome
    (95% confidence intervals)
    Occupational groupsNumber * UnadjustedAge-adjusted
    Overall male workers
    1,859/13,152,179
    24.1 (21.7–26.5)
    23.2 (21.0–25.5)
    Non-manual workers
    676/4,905,005
    26.3 (22.3–30.2)
    26.4 (22.3–30.5)
      Managers
    61/362,106
    31.7 (18.1–45.3)
    26.5 (14.2–38.8)
      Professional and related workers
    335/2,531,917
    25.0 (19.3–30.8)
    27.3 (20.9–33.6)
      Clerks
    280/2,010,981
    26.9 (21.0–32.8)
    24.6 (18.1–31.1)
    Service/sales workers
    304/2,302,276
    19.9 (14.6–25.2)
    21.5 (15.9–27.1)
      Service workers
    104/910,156
    15.7 (8.1–23.3)
    17.5 (9.0–26.0)
      Sales workers
    200/1,392,120
    22.7 (15.3–30.0)
    23.0 (16.2–29.8)
    Manual workers
    879/5,944,897
    23.9 (20.6–27.1)
    20.1 (17.3–23.0)
      Skilled agricultural, forestry and fishery workers
    272/1,589,656
    24.3 (18.2–30.4)
    15.6 (10.9–20.2)
      Craft and related trades workers
    206/1,733,288
    15.7 (10.6–20.7)
    16.4 (11.0–21.9)
      Equipment, machine operating and assembling workers
    240/1,597,780
    35.4 (28.4–42.4)
    26.5 (21.1–32.0)
      Elementary workers
    161/1,024,171
    19.2 (11.3–27.2)
    16.9 (9.4–24.4)
    Overall female workers
    1,544/8,824,612
    17.3 (14.8–19.8)
    19.5 (17.3–21.6)
    Non-manual workers
    545/3,325,220
    7.7 (4.4–10.9)
    20.8 (11.3–30.2)
      Managers
    8/22,859
    12.8 (−9.1–34.8)
    10.6 (−6.7–27.9)
      Professional and related workers
    334/1,998,628
    7.3 (3.5–11.2)
    27.9 (21.5–34.3)
      Clerks
    203/1,303,732
    8.1 (2.6–13.5)
    9.8 (2.7–16.9)
    Service/sales workers
    428/2,502,853
    16.9 (12.8–20.9)
    18.4 (13–22.9)
      Service workers
    215/1,340,314
    16.9 (11.4–22.3)
    20.5 (14.5–26.6)
      Sales workers
    213/1,162,539
    16.9 (11.2–22.5)
    17.6 (11.9–23.2)
    Manual workers
    581/2,996,538
    28.4 (23.9–32.9)
    20.8 (16.9–24.7)
      Skilled agricultural, forestry and fishery workers
    225/1,011,474
    39.2 (31.8–46.6)
    22.0 (15.2–28.9)
      Craft and related trades workers
    42/258,235
    19.1 (4.4–33.8)
    12.0 (2.8–21.2)
      Equipment, machine operating and assembling workers
    35/158,745
    7.8 (−2.5–18.1)
    6.2 (−1.7–14.2)
      Elementary workers279/1,568,08325.0 (19.1–31.0) 20.0 (14.5–25.5)
     
    Non-manual workers
    Service/sales workers
    Manual workers
     
    ComponentsManagersProfessional and related workersClerksService workersSales workersSkilled agricultural, forestry and fishery workersCraft and related trades workersEquipment, machine operation and assembling workersElementary workersTotalp-value
    Male workers
     
     
     
     
     
     
     
     
     
     
     
      WC ≥ 90 cm (M)/80 cm (W)
     
    24.5 (2.5)
     
    28.6 (3.5)
     
    24.0 (1.9)
     
    25.1 (1.3)
    0.946
    35.4 (8.7)
    21.1 (2.8)
    25.7 (3.7)
    25.7 (4.7)
    28.2 (3.9)
    22.8 (3.5)
    31.1 (4.3)
    31.0 (3.2)
    18.2 (4.2)
    0.705
      BP ≥ 130/85 mmHg or treated
     
    40.1 (2.5)
     
    33.3 (3.3)
     
    32.7 (1.7)
     
    36.3 (1.4)
    0.036
    46.0 (6.9)
    33.2 (3.5)
    51.6 (2.6)
    29.8 (4.4)
    35.5 (3.8)
    26.6 (3.3)
    29.0 (3.5)
    32.7 (2.6)
    36.2 (4.1)
    <0.001
      TG ≥ 150 mg/dl
     
    39.4 (2.6)
     
    35.5 (2.7)
     
    35.3 (2.2)
     
    37.4 (1.4)
    0.225
    41.8 (8.0)
    43.9 (3.3)
    33.7 (3.8)
    35.2 (5.0)
    37.7 (3.3)
    25.9 (4.6)
    34.7 (4.0)
    44.9 (2.9)
    29.9 (4.9)
    0.119
      HDL-C < 40 mg/dl
     
    20.5 (2.2)
     
    13.3 (2.5)
     
    18.3 (1.8)
     
    19.2 (1.2)
    0.024
    14.9 (4.1)
    22.0 (3.2)
    16.9 (2.5)
    12.6 (3.8)
    13.5 (3.0)
    9.0 (1.5)
    17.1 (3.0)
    19.5 (2.9)
    18.8 (4.6)
    0.119
      FPG ≥ 100 mg/dl or treated
     
    31.8 (2.5)
     
    29.3 (3.4)
     
    26.2 (1.7)
     
    28.6 (1.3)
    0.191
    31.2 (7.6)
    31.8 (3.2)
    34.5 (4.1)
    26.2 (5.1)
    29.2 (3.8)
    20.3 (2.4)
    25.8 (3.5)
    27.1 (2.8)
    26.8 (3.4)
    0.284
    Female workers
     
     
     
     
     
     
     
     
     
     
      WC ≥ 90 cm (M)/80 cm (W)
     
    34.6 (4.8)
     
    39.0 (2.5)
     
    41.8 (3.3)
     
    36.8 (1.4)
    <0.001
    19.5 (12.2)
    41.8 (3.4)
    24.6 (4.3)
    42.0 (3.4)
    36.9 (3.2)
    50.5 (6.7)
    32.0 (5.1)
    22.4 (5.4)
    40.9 (5.0)
    <0.001
      BP ≥ 130/85 mmHg or treated
     
    21.0 (1.8)
     
    23.8 (2.2)
     
    27.6 (1.9)
     
    25.6 (1.2)
    <0.001
    29.4 (10.8)
    19.0 (2.2)
    23.2 (3.3)
    26.4 (2.9)
    21.3 (3.0)
    29.0 (4.2)
    32.3 (4.8)
    7.1 (4.0)
    27.0 (2.5)
    <0.001
      TG ≥ 150 mg/dl
     
    15.7 (2.7)
     
    23.3 (2.9)
     
    17.6 (2.1)
     
    17.9 (1.1)
    <0.001
    31.8 (13.2)
    18.4 (2.1)
    5.6 (2.0)
    22.7 (4.5)
    23.6 (3.4)
    16.1 (2.6)
    9.5 (4.0)
    8.3 (4.8)
    18.4 (2.8)
    <0.001
      HDL-C < 50 mg/dl
     
    34.9 (4.7)
     
    32.2 (2.9)
     
    34.7 (3.1)
     
    32.8 (1.4)
    <0.001
    15.1 (10.8)
    43.0 (2.6)
    21.2 (4.3)
    33.2 (3.6)
    33.0 (4.0)
    43.0 (5.8)
    37.9 (8.4)
    16.8 (5.1)
    32.1 (5.1)
    <0.001
      FPG ≥ 100 mg/dl or treated 
    19.8 (4.5)
     
    16.1 (1.9)
     
    19.0 (2.0)
     
    18.1 (1.1)<0.001
    9.4 (8.6)24.7 (3.7)15.6 (3.5)15.3 (3.1)17.1 (2.8)14.9 (1.8)9.0 (2.2)15.2 (5.8)20.7 (2.5)<0.001
     
    Odds ratio (95% confidence intervals)
     MaleFemale
    Model I*
     
     
    Occupational group
     
     
     Non-manual workers
    1.00 (reference)
    1.00 (reference)
      Service/sales workers
    0.66 (0.42–1.02)
    0.98 (0.45–2.12)
      Service workers
    0.49 (0.25–0.96)
    0.92 (0.36–2.32)
      Sales workers
    0.74 (0.43–1.28)
    1.12 (0.51–2.46)
     Manual workers
    0.62 (0.44–0.88)
    1.00 (0.46–2.16)
      Skilled agricultural, forestry and fishery workers
    0.38 (0.20–0.70)
    1.56 (0.56–4.33)
      Craft and related trades workers
    0.39 (0.23–0.66)
    0.78 (0.21–2.83)
      Equipment, machine operating and assembling workers
    1.22 (0.82–1.83)
    0.88 (0.16–4.67)
      Elementary workers
    0.43 (0.21–0.91)
    0.84 (0.38–1.86)
    Model II
     
     
    Occupational groups
     
     
     Non-manual workers
    1.00 (reference)
    1.00 (reference)
      Service/sales workers
    0.63 (0.39–0.99)
    1.04 (0.48–2.25)
      Service workers
    0.45 (0.22–0.93)
    0.98 (0.39–2.47)
      Sales workers
    0.73 (0.42–1.26)
    1.16 (0.53–2.57)
     Manual workers
    0.59 (0.41–0.85)
    1.02 (0.47–2.21)
      Skilled agricultural, forestry and fishery workers
    0.37 (0.20–0.69)
    1.54 (0.56–4.25)
      Craft and related trades workers
    0.37 (0.22–0.63)
    0.78 (0.22–2.81)
      Equipment, machine operating and assembling workers
    1.16 (0.77–1.75)
    0.90 (0.17–4.87)
      Elementary workers0.42 (0.19–0.91)0.87 (0.39–1.94)
    Table 1 Demographic characteristics by major category of the Korean Standard Classification of Occupations among male workers

    *Estimated mean (standard error).

    Table 2 Demographic characteristics by major category of the Korean Standard Classification of Occupations among female workers

    *Estimated mean (standard error).

    Table 3 The prevalence of the metabolic syndrome according to demographic characteristics

    *Subject number/estimated population number. Subject number varies due to item which was not answered. Unadjusted prevalence of the metabolic syndrome (95% confidence intervals).

    Table 4 Unadjusted and age-adjusted prevalence of the metabolic syndrome by category of the Korean Standard Classification of Occupations stratified by gender

    *Subject number/estimated population number. The prevalence estimate for each occupational group was above the upper bound of the 95% confidence interval for the overall prevalence estimate.

    Table 5 Age-adjusted prevalence of the components of the metabolic syndrome by category of the Korean Standard Classification of Occupations

    Abbreviation: All values were the estimated percentage (standard error). WC waist circumference, BP blood pressure, TG triglyceride, HDL-C high-density lipoprotein cholesterol, FPG fasting plasma glucose, M male, F female.

    Table 6 Multiple logistic regression to assess the relationship between occupation and meeting criteria for the metabolic syndrome among Korean workers aged ≥20 years

    * Model I: Adjusted for age, level of education, household income, high-risk drinking, smoking status, and vigorous physical activity.

    Model II: Adjusted for Model I factors, plus work hours, and work schedule.


    Ann Occup Environ Med : Annals of Occupational and Environmental Medicine
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