Working hours and depressive symptomatology among full-time employees: Results from the fourth Korean National Health and Nutrition Examination Survey (2007-2009).

OBJECTIVE: This study aimed to examine the distribution of working hours and the association between working hours and depressive symptomatology using representative data from a national, population-based survey. METHOD: Data came from the fourth Korean National Health and Nutrition Examination Survey (2007-2009), which employed a systematic, stratified cluster-sampling method. We used logistic regression procedures to estimate the importance of weekly working hours as a predictor of depressive symptomatology. RESULTS: The prevalence of depressive symptomatology was 10.2%. The work week, which averaged 48.3 hours for the sample as a whole, was longer for men (49.8 hours) than women (45.3 hours), and 12.1% of respondents were engaged in shift work. In logistic regression analyses, compared to those working < 52 hours per week, the odds ratios (OR) of working hours as a predictor of depressive symptomatology were 1.19 [95% confidence interval (95% CI) 0.77-1.85] for those working 52-59 hours per week and 1.62 (95% CI 1.20-2.18) for those working ≥ 60 hours per week, after adjustment for demographic characteristics, health behaviors, socioeconomic status, employment status, and work schedules. It showed a positive dose-response relationship between working hours and depressive symptomatology (P = 0.0059). CONCLUSIONS: Working hours in Korea are long. There is an association between working hours and depressive symptomatology, and there seems be a trend in working hours and depressive symptomatology.

The relationship of liver function tests to mixed exposure to lead and organic solvents.

OBJECTIVE: This study aims to compare liver function indices (aspartate aminotransferase [AST], alanine aminotransferase [ALT], and gamma glutamyl transferase [GGT]) among males who work with lead, organic solvents, or both lead and organic solvents, under the permissible exposure limit (PEL). METHODS: A total of 593 (out of 2,218) male workers who agreed to share their personal health information for medical research were selected for this study. Those excluded were hepatitis B carriers, individuals exposed to occupational risk factors other than lead and organic solvents, and individuals without liver function results. The 593 were divided into five groups: a lead-exposed group, an organic solvent-exposed group exposed to trichloroethylene (TCE co-exposed solvent group), an organic solvent-exposed group not exposed to trichloroethylene (TCE non-exposed solvent group), a lead and organic solvent-exposed group (mixed exposure group), and a non-exposed group (control group).We performed a one way-analysis of variance (one way-ANOVA) test to compare the geometric means of liver function indices among the groups, using a general linear model (GLM) to adjust for age, work duration, body mass index (BMI), smoking, and alcohol intake. In addition, we performed a binary logistic regression analysis to compare the odds ratios among groups with an abnormal liver function index, according to a cut-off value. RESULTS: The ALT and AST of the mixed exposure group were higher than those of the other groups. The GGT of the mixed exposure group was higher than the TCE co-exposed solvent group, but there was no difference among the control group, TCE non-exposed solvent group, lead-exposed group, and mixed exposure group. The same result was evident after adjusting by GLM for age, work duration, BMI, smoking, and alcohol intake, except that ALT from the mixed exposure group showed no difference from the TCE co-exposed solvent group.When the cut-off values of the AST, ALT, and GGT were 40 IU/L, 42 IU/L, and 63 IU/L, respectively, a logistic regression analysis showed no differences in the odds ratios of those who had an abnormal liver function index among the groups. However, if the cut-off values of the AST, ALT, and GGT were 30 IU/L, 30 IU/L, and 40 IU/L, respectively, the odds ratio of the AST in the mixed exposure group was 4.39 (95% CI 1.86-10.40) times higher than the control. CONCLUSION: This study indicates that a mixed exposure to lead and organic solvents is dangerous, even if each single exposure is safe under the permissible exposure limit. Therefore, to ensure occupational health and safety in industry, a continuous efforts to study the effects from exposure to mixed chemicals is needed.