Mo-Yeol Kang

Long working hours and cardiovascular disease: a meta-analysis of epidemiologic studies.

Objective: To conduct a meta-analysis from published studies to evaluate the relationship between long working hours and the risk of cardiovascular disease (CVD). Methods: Among a total of 341 published studies found from publicly accessible databases, five cohort studies and six case–control studies were analyzed for the study. Results: Statistically significant heterogeneity has been observed (P = 0.037). The effect of longer working hours was significantly associated with the risk of CVD in the random-effects model of all 11 studies (odds ratio, 1.37; 95% confidence interval, 1.11 to 1.70). On the basis of meta-regression analysis, the result was not affected by the mean age, region, or the study year. The P value using Eager test was 0.701 suggesting this analysis was unlikely to have any publication bias. Conclusions: These findings provide evidence of increased CVD with long working hours.

Effects of environmental cadmium exposure on liver function in adults

Background There is inconsistency regarding the effects of cadmium exposure on liver function between the positive results found in animal studies and the negative results highlighted in epidemiological studies. We investigated whether environmental cadmium exposure is associated with an elevation in serum liver enzyme activity in Korean adults. Methods This cross-sectional study evaluated adult participants without liver disease from the Korean National Health and Nutrition Examination Survey for 2008–2009. Multiple linear regression was conducted to investigate the association between blood cadmium concentration and the serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) adjusting for age, sex, body mass index and the amount of alcohol consumption. Subjects were stratified into quartiles by their cumulative cadmium exposure rank. We estimated the multivariate-adjusted ORs for liver enzyme elevation using logistic regression models with the first quartile as the reference group. Results Total number of the subjects in the analysis was 3914. The blood cadmium concentrations were significantly associated with liver enzyme levels (AST, β=2.677, p value <0.0001; ALT, β=3.696, p value <0.0001; ALP, β=11.730, p value <0.0001). As the cadmium levels approached higher quartiles, the ORs for an elevated AST, ALT and ALP was increased significantly. Conclusions Environmental cadmium exposures are associated with an elevation in serum liver enzyme levels in Korean adults.

Effect of Long Working Hours on Self-reported Hypertension among Middle-aged and Older Wage Workers

ObjectivesMany studies have reported an association between overwork and hypertension. However, research on the health effects of long working hours has yielded inconclusive results. The objective of this study was to identify an association between overtime work and hypertension in wage workers 45 years and over of age using prospective data.MethodsWage workers in Korea aged 45 years and over were selected for inclusion in this study from among 10,254 subjects from the Korean Longitudinal Study of Ageing. Workers with baseline hypertension and those with other major diseases were excluded. In the end, a total of 1,079 subjects were included. A Cox proportional hazards model was used to calculate hazard ratios and adjust for baseline characteristics such as sex, age, education, income, occupation, form of employment, body mass index, alcohol habit, smoking habit, regular exercise, and number of working days per week. Additional models were used to calculate hazard ratios after gender stratification.ResultsAmong the 1,079 subjects, 85 workers were diagnosed with hypertension during 3974.2 person-months. The average number of working hours per week for all subjects was 47.68. The proportion of overtime workers was 61.0% (cutoff, 40 h per week). Compared with those working 40 h and less per week, the hazard ratio of subjects in the final model, which adjusted for all selected variables, working 41-50 h per week was 2.20 (95% confidence interval [CI], 1.19–4.06), that of subjects working 51-60 h per week was 2.40 (95% CI, 1.07–5.39), and that of subjects working 61 h and over per week was 2.87 (95% CI, 1.33–6.20). In gender stratification models, the hazard ratio of the females tended to be higher than that of the males.ConclusionAs the number of working hours per week increased, the hazard ratio for diagnosis of hypertension significantly increased. This result suggests a positive association between overtime work and the risk of hypertension.

Long working hours may increase risk of coronary heart disease

OBJECTIVE To evaluate the association between long working hours and risk of coronary heart disease (CHD) estimated by Framingham risk score (FRS) in Korean adults. METHODS This study evaluated adult participants in Korean National Health and Nutrition Examination Survey IV (2007-2009). After inclusion and exclusion criteria were applied, the final sample size for this study model was 8,350. Subjects were asked about working hours and health status. Participants also completed physical examinations and biochemical measurement necessary for estimation of FRS. Multiple logistic regression was conducted to investigate the association between working hours and 10-year risk for CHD estimated by FRS. RESULTS Compared to those who work 31-40 hr, significantly higher 10-year risk was estimated among subjects working longer hours. As working hours increased, odds ratio (OR) for upper 10 percent of estimated 10-year risk for CHD was increased up to 1.94. CONCLUSIONS Long working hours are significantly related to risk of coronary heart disease.

Is suicidal ideation linked to working hours and shift work in Korea

Is suicidal ideation linked to working hours and shift work in Korea? : Chang‐Gyo Yoon, et al. Department of Preventive Medicine, Armed Forces Medical Command, Republic of Korea

Influence of illness and unhealthy behavior on health-related early retirement in Korea: Results from a longitudinal study in Korea

Influence of illness and unhealthy behavior on health‐related early retirement in Korea: Results from a longitudinal study in Korea: Mo‐Yeol KANG, et al. Institute for Occupational and Environmental Health, Wonjin Green Hospital, Republic of Korea—

Gender and educational level modify the relationship between workplace mistreatment and health problems: a comparison between South Korea and EU countries

Gender and educational level modify the relationship between workplace mistreatment and health problems: a comparison between South Korea and EU countries: Minsang Yoo, et al. Department of Preventive Medicine, College of Medicine, Seoul National University, Republic of Korea

Association between voluntary/involuntary job loss and the development of stroke or cardiovascular disease: a prospective study of middle-aged to older workers in a rapidly developing Asian country.

Background The aim of this research was to investigate the association between job loss and the development of stroke or cardiovascular disease among middle-aged to older individuals in Korea. We also examined how this relationship was modified by gender and the nature of the job loss. Methods This study used samples from the first- to fourth-wave datasets from the Korean Longitudinal Study of Aging (KLoSA), which were collected in 2006, 2008, 2010, and 2012. The study collected data from a total of 10,254 subjects aged ≥45 years at baseline. After applying exclusion criteria, the final sample size for analysis consisted of 4,000 individuals. Information about employment status, development of stroke or cardiovascular disease, and covariates (age, income level, and behavioral factors) was obtained. Cox proportional hazards models were used to evaluate the association between voluntary/involuntary job loss and the development of stroke or cardiovascular disease. We performed these analyses separately according to disease, gender, and the nature of the job loss. Results Involuntary job loss significantly increased the risk of stroke or cardiovascular disease among males (adjusted hazard ratio [HR] = 3.560, 95% confidence interval [CI] = 2.055–6.168). Voluntary retirement also increased the risk of cardiovascular disease or stroke among males (adjusted HR = 2.879, 95% CI = 1.533–5.409). Job loss was more closely associated with stroke than with cardiovascular disease (stroke, adjusted HR = 6.208, 95% CI = 2.417–15.943; cardiovascular disease, adjusted HR = 2.768, 95% CI = 1.402–5.465). Conclusion Our findings suggest that both voluntary retirement and involuntary job loss increase the risk for stroke or cardiovascular disease in middle-aged to older individuals, especially males.

Effects of perceived job insecurity on depression, suicide ideation, and decline in self-rated health in Korea: a population-based panel study

PurposeTo investigate the effects of job security on new development of depressive episode, suicide ideation, and decline in self-rated health.MethodsData from the Korea Welfare Panel Study from 2012 to 2015 were analysed. A total of 2912 waged workers self-assessed their depressive episode, suicide ideation, and health annually by answering the questionnaire. Participants were divided into three groups according to the level of job security: high, intermediate and low. To evaluate the influence of job security, we performed survival analysis after stratification by gender with adjustment for covariates. The result was further stratified by whether the respondent was the head of household.ResultsAfter adjusting for covariates, men in low job security group showed significantly higher hazard ratios (HRs) for depression (HR 1.27, 95% CI 1.01–1.60), suicide ideation (HR 3.25, 95% CI 1.72–6.16), and decline in self-rated health (HR 1.73, 95% CI 1.16–2.59). Women showed significantly higher HR of depression in the intermediate (HR 1.37, 95% CI 1.01–1.87) and low (HR 1.50, 95% CI 1.12–1.99) job security group. Male head of household with low job security showed significantly higher HR of depression, suicide ideation, and decline in self-rated health. Non-head-of-household women with intermediate and low job security showed higher risk of depression than those with high job security.ConclusionsWe found that perceived job insecurity is associated with the new development of depressive episode, suicide ideation, and decline in self-rated health.

The crossover effect of spouses’ long working hours on depressive symptoms and suicidal ideation

To examine the association between spouses’ weekly working hours (SWWH) and psychological symptoms such as depressive symptom and suicidal ideation. We used data from the fourth and fifth Korean National Health and Nutrition Examination Survey (2007–2012). We collected information about general characteristics, depressive symptoms, suicidal ideation, and working hours. After inclusion and exclusion criteria were applied, a sample of 8,056 house units was used for analysis. A multiple logistic regression was conducted to investigate the association between SWWH and depressive symptoms, as well as suicidal ideation, to estimate the odds ratio (OR). The relationship between SWWH and psychological symptoms were linear in husbands, and J-shaped in wives. ORs for husbands’ depressive symptoms and suicidal ideation increased according to increase in SWWH (p-values for trend were 0.0045 and <0.001, respectively). Crude ORs for wives’ depressive symptoms and suicidal ideation decreased until SWWH of 40 to 49 hours, but increased after SWWH of 40 to 49 hours (all p-values were below 0.01). Similar trends were observed after adjustment for age, obesity, household income, and one’s own weekly working hours, up to 1.33 and 1.57 in husbands, and 1.29 and 1.32 in wives, respectively. SWWH is negatively associated with mental health.