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

Given limited prior research, especially with small samples, this study examined the association between abnormal workplace temperature exposure and depressive symptoms among Korean employees. Here, workplace temperature exposure was operationalized as self-reported heat or cold exposure time, and the outcome was WHO-5 screen-positive depressive symptoms. The fifth Korean Working Conditions Survey (KWCS), conducted in 2017, included 30,108 paid employees; the primary common complete-case analysis included 29,413 participants. Heat and cold exposure time were categorized as none, low, intermediate, or high, and a WHO-5 score ≤ 28 defined screen-positive depressive symptoms. Survey-weighted modified Poisson regression with respondent-level empirical sandwich covariance estimated prevalence ratios (PRs) and 95% confidence intervals (CIs). The survey-weighted prevalence was 11.07%. In the primary adjusted model (Model 2), the categorical patterns were non-monotonic. Compared with no exposure, adjusted PRs for high heat and high cold exposure time were 1.04 (95% CI 0.88–1.24) and 1.15 (0.95–1.39), respectively. Formal interaction tests provided no evidence of effect modification by sex or broad occupational group. Due to the cross-sectional design, causal relationships cannot be established. The high-exposure confidence intervals included one; the findings therefore warrant cautious interpretation. Workplace thermal comfort remains relevant to worker well-being, while prospective studies with objective exposure measurements are needed.