Long Hours in Hot or Cold Workplaces Show No Clear Link to Depressive Symptoms in Korean Workers

A nationwide analysis of more than 29,000 South Korean employees has found no clear association between the amount of time workers report spending in hot or cold workplace conditions and screen-positive depressive symptoms, according to a cross-sectional study published in Scientific Reports. Researchers drew on the fifth Korean Working Conditions Survey, conducted in 2017, which included 30,108 paid employees; the primary complete-case analysis covered 29,413 participants. Workplace temperature exposure was operationalized as self-reported time spent in heat or cold, categorized as none, low, intermediate, or high.

Depressive symptoms were screened using the WHO-5 well-being index, with a score of 28 or below defining screen-positive symptoms. The survey-weighted prevalence of screen-positive depressive symptoms was 11.07 percent across the analyzed sample. The team used survey-weighted modified Poisson regression with respondent-level empirical sandwich covariance to estimate prevalence ratios and 95 percent confidence intervals, adjusting for a range of covariates in their primary model.

In that primary adjusted model, the patterns across exposure categories were non-monotonic, meaning the estimated associations did not rise steadily with increasing exposure time. Compared with workers reporting no exposure, the adjusted prevalence ratio for high heat exposure time was 1.04 (95 percent confidence interval 0.88 to 1.24), and for high cold exposure time it was 1.15 (95 percent confidence interval 0.95 to 1.39). Because both confidence intervals included the null value of one, the study could not rule out the absence of any association at the highest exposure levels.

The authors emphasize that these findings warrant cautious interpretation for precisely this reason. Formal interaction tests found no evidence that sex or broad occupational group modified the relationship between temperature exposure and depressive symptoms, suggesting the broadly null pattern held across these subgroups in this dataset. The study's design imposes an important limitation: as a cross-sectional survey capturing exposure and outcome at the same time, it cannot establish causal relationships.

The authors note that prior research in this area has been limited, particularly by small samples, which makes this large nationwide dataset a meaningful contribution despite its null-to-weak findings. They conclude that workplace thermal comfort remains relevant to worker well-being and call for prospective studies with objective exposure measurements to clarify whether abnormal workplace temperatures affect mental health over time.

Subject of Research: Association between self-reported workplace heat and cold exposure and depressive symptoms among Korean employees

Article Title: Self-reported workplace heat and cold exposure time and WHO-5 screen-positive depressive symptoms among Korean employees: a nationwide cross-sectional study

Article References: Kim, S.-K., Kim, J.-Y., Kim, J., Yoon, J.-H., & Yong, S. Y. (2026). Self-reported workplace heat and cold exposure time and WHO-5 screen-positive depressive symptoms among Korean employees: a nationwide cross-sectional study. Scientific Reports. https://doi.org/10.1038/s41598-026-76782-5

Image Credits: AI Generated

DOI: 10.1038/s41598-026-76782-5

Keywords: occupational health, heat exposure, cold exposure, depressive symptoms, WHO-5, Korean Working Conditions Survey, cross-sectional study, workplace thermal comfort, mental health, epidemiology, Self-reported, workplace