The relationship between night work and involuntary weight change: data from the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010–2012)

BACKGROUND: Previous studies on the association between shift or night work and weight change have been focused on finding the risk of weight gain caused by shift or night work. In this study, we aimed to reveal the risk of weight gain and weight loss associated with night work by using a nationwide representative data. METHODS: This study was performed on 1605 full-time wage workers between the age of 20 and 69 based on the fifth Korea National Health and Nutrition Examination Survey (KNHANES 2010–2012). The association between night work and involuntary weight change in the previous year was divided into the categories of weight gain and weight loss and studied with modifications in socio-demographic variables, health behavior-related variables, and occupational characteristic variables. RESULTS: The participants working in night work accounted for 10.6 % of total study participants (male; 11.9 %, female 7.4 %). Workers who worked more than 48 hours per week on average accounted for 41.6 % of the total study participants (male; 46.3 %, female 29.1 %). Odds ratio (OR) of weight loss associated with night work in male workers was 0.34 (95 % confidence interval (CI) 0.16–0.76) after controlling for several related factors. OR of weight loss associated with night work in female workers with long working hours was 1.95 (95 % CI 0.47–80.86) and that of weight gain was 2.83 (95 % CI 0.12–69.83) after adjusting associated factors. CONCLUSIONS: In this cross-sectional study with national representative sample, night work may lower the risk of weight loss in male workers and induce weight change (weight loss or weight gain) in female workers with long working hours. Therefore, future studies with cohort study design for night workers are needed to reveal the mechanisms and health effects of weight change associated with night work and establish proper management solutions with health and labor policies for Korean night workers.

The Association between Long Working Hours and Self-Rated Health

OBJECTIVES: This study was conducted to determine the number of hours worked per week by full-time wage workers by using the data of the Korean Labor and Income Panel Study (KLIPS), which represents the domestic urban area household, and to determine the association between weekly working hours and the level of self-rated health. METHODS: We used data from the 11th KLIPS conducted in 2008. The subjects of this study were 3,699 full-time wage workers between the ages of 25 and 64 years. The association between weekly working hours and self-rated health was analyzed considering socio-demographic characteristics, work environment, and health-related behaviors. RESULTS: Among the workers, 29.7% worked less than 40 hours per week; 39.7%, more than 40 to 52 hours; 19.7%, more than 52 to 60 hours; and 10.9%, more than 60 hours per week. After controlling for socio-demographic variables, work environment-related variables, and health-related behavior variables, the odds ratio (OR) for poor self-rated health for the group working more than 40 hours and up to 52 hours was calculated to be 1.06 (95% confidence interval (CI), 0.89-1.27) when the group working less than 40 hours per week was considered the reference. The OR for the group working more than 60 hours was 1.42 (95% CI, 1.10-1.83) and that for the group working more than 52 hours and up to 60 hours was 1.07 (95% CI, 0.86-1.33). After stratification by gender and tenure, the OR of the female workers group and that of the group with a tenure of more than 1 year were found to be significantly higher than those of the other groups. CONCLUSIONS: This study showed that workers working more than 60 hours per week have a significantly higher risk of poor self-rated health than workers working less than 40 hours per week. This effect was more obvious for the female workers group and the group with a tenure of more than 1 year. In the future, longitudinal studies may be needed to determine the association between long working hours and various health effects in Korean workers.

The Association between Shift Work and Bone Mineral Density : analysis of 2008-2009 Korean National Health and Nutrition Examination Survey / 대한산업의학회지

OBJECTIVES: The objectives of this study were to explore the association between shift work and the bone mineral density in a representative sample of Korean workers. METHODS: He data from the Fourth Korean National Health and Nutrition Examination Survey (2008-2009) was used. The participants were Korean workers aged 16 to 60 years. Logistic regression analysis was applied to determine the association between shift work and the bone mineral density after controlling for covariates using the SAS version 9.3 package program. RESULTS: The blood vitamin D level in shift workers was significantly lower than that of day workers in both males and females. In male shift workers, shift work was significantly associated with a decreased bone mineral density in the femoral neck (odds ratio(OR) 1.42, 95% confidence interval(CI)=1.05~1.92) and lumbar spine (OR 1.53, 95% CI=1.09~2.15) compared to day workers. After controlling for covariates, this association was still significant. In the case of female shift workers, shift work was significantly related to a decreased bone mineral density in the total femur (OR 2.84, 95% CI=1.69~4.79) and lumbar spine (OR 1.58, 95% CI=1.12~2.24). After controlling for covariates, this risk was not statistically significant. CONCLUSIONS: The blood vitamin D level of shift workers was significantly lower than that of day workers. In male shift workers, shift work can decrease the bone mineral density in the femoral neck and lumbar spine. Prospective studies with information on the shift work intensity and duration and exposuredata to explain mechanisms will be needed.