Comparing risk of depression between day and night/shift workers using the PHQ-9: a study utilizing the 2014, 2016, and 2018 Korea National Health and Nutrition Examination Survey data

Night shift work, genetic risk, and the risk of depression: A prospective cohort study

BACKGROUND

Genetic factors and night shift work both contribute to the risk of depression, but whether the association of night shift work with depression varies by genetic predisposition remains unclear.

OBJECTIVES

To assess whether night shift work is associated with a higher risk of depression regardless of genetic predisposition.

METHODS

We used data from the UK biobank of 247,828 adults aged 38-71 free of depression at baseline from March 13, 2006, to October 1, 2010. Genetic predisposition to depression was assessed using polygenic risk scores (PRS) weighted sums of genetic variant indicator variables and classified as low (lowest tertile), intermediate (tertile 2), and high (highest tertile). Night shift work exposures were collected using a touchscreen questionnaire and were divided into four categories.

RESULTS

After a median follow-up of 12.7 years, 7315 participants developed depression. Compared with day workers, HRs (95 % CIs) of depression were 1.28 (1.19-1.38) for shift work, but never or rarely night shifts, 1.32 (1.20-1.45) for irregular night shifts, and 1.20 (1.07-1.34) for permanent night shifts. Considering lifetime employment and compared with never shift workers, >8 nights/month (HR: 1.40; 95 % CI: 1.19-1.66) and <10 years (HR: 1.30; 95 % CI: 1.09-1.54) of night shift work were associated with a higher risk of depression. In joint effect analyses, compared to participants with low genetic predisposition and day workers, the HRs (95 % CIs) of depression were 1.49 (1.32-1.69) in those with high genetic predisposition and shift work, but never or rarely night shifts, and 1.36 (1.20-1.55) for those with high genetic predisposition and irregular/permanent night shifts. In addition, there was neither multiplicative nor additive interaction between genetic predisposition and night shift work on the risk of depression.

CONCLUSIONS

Night shift work was associated with an increased risk of depression regardless of genetic risk.

Changes in the Health Indicators of Hospital Medical Residents During the Four-Year Training Period in Korea

BACKGROUND

In South Korea, the legal maximum working hours per week for medical residents is 88 hours, which are longer than those for other occupations, and the intensity of the workload is also remarkably high. Long working hours and job-related stress can worsen the health status of residents. This study aimed to analyze the four-year annual health checkup (AHC) data of residents to identify changes in their health indicators.

METHODS

This study included 457 male residents who received 4 years of training at a university hospital. They underwent an AHC every year during the training period. Changes in health indicators and related factors over the 4 years were investigated.

RESULTS

Body mass indices (BMI), blood pressures (BPs), liver function test (LFT) results, and total cholesterol (TC) levels were significantly worsened during the training period. The increases were the highest in the early training years, between the 2^nd and 1^st AHC. The working hours of the fourth-year residents were the shortest and showed low smoking and drinking rates and high regular exercise rates. On comparing by department, surgical residents showed the highest increases in BMI, diastolic BP, and fasting blood glucose (FBG), LFT enzyme, and TC levels during the training period, compared to residents from the medical and clinical support departments. Residents who were working ≥ 80 hours showed significantly higher FBG and LFT enzyme levels than those working < 80 hours.

CONCLUSION

This study is meaningful as it is the first study in Korea to investigate the changes in the health of residents through objective health indicators. The possibility of the 4-year training period adversely affecting the health of residents was confirmed. Health indicators were significantly worsened, especially in the early training period, in surgical residents, and in residents who worked for long hours. Efforts are needed to restrict long working hours and distribute workload during the 4-year training period.