Associations of sitting time and occupation with metabolic syndrome in South Korean adults: a cross-sectional study

Background: Previous evidence suggests that there is a correlation between prolonged sitting time and cardio-metabolic disease, such as metabolic syndrome (MS). Cardiovascular disease is the second-leading cause of mortality in South Korea, a country with the longest working hours among all member states of the Organization for Economic Co-operation and Development. However, no previous study has investigated the relationships of overall sitting-time and occupation with MS in South Korea. Accordingly, the present study examined these relationships in a South Korean population. Methods: Data from the sixth Korean National Health and Nutrition Examination Survey (KNHANES), a nationally representative survey with a cross-sectional design, were used in the present study. MS diagnoses were evaluated using the International Diabetes Foundation (IDF) criteria. Participants self-reported their overall sitting times, and occupations were classified using the Korean version of the Standard Classification of Occupations (KSCO). A multiple logistic regression analysis was conducted to evaluate the associations of sitting time and occupation with MS. Results: The risk of MS was 1.21-fold higher among participants who sat for > 7 h/day than among those who sat for <= 7 h/day (odds ratio [OR]: 1.21, 95 % confidence interval [CI]: 1.00-1.46). Regarding occupation, office workers had a two-fold higher risk of MS than did agriculture, forestry, and fishery (AFF) workers (OR: 2.01, 95 % CI: 1.26-3.22). In a combined analysis of sitting time and occupation, male participants who sat for > 7 h/day and reported an occupation that involves office work (OW) or machine fitting (MF) were significantly more likely to have MS when compared to those who sat for <= 7 h/day and were employed as AFF workers (> 7 h/day x OW, OR: 2.41, 95 % CI: 1.05-5.51; > 7 h/day x MF, OR: 2.92, 95 % CI: 1.43-5.93). Conclusions: Excessive sitting time and a sedentary occupation correlated positively with MS in South Korean adults. Accordingly, a reduction in the overall sitting time or inclusion of energy-expending activities in the workplace might improve the rate of MS.