Perceived indoor thermal environment and depressive symptoms among older adults in the Japan Gerontological Evaluation Study.

Depression is a major global health problem and presents a significant health burden. Although abnormal indoor temperatures are known to be associated with adverse health effects, their link to depression is unclear, especially regarding indoor heat. This study aimed to examine the association between perceived indoor cold or heat and depressive symptoms among Japanese older adults. We used cross-sectional data from the 2022 Japan Gerontological Evaluation Study (JAGES), targeting independent older adults aged ≥ 65 years. The prevalence of depressive symptoms was the dependent variable, while the participants' self-reported ability of their housing to prevent indoor cold or heat was the independent variable. Prevalence ratios (PRs) and 95% confidence intervals (CIs) were estimated using Poisson regression models with potential confounders as covariates. Additionally, we conducted a stratified analysis by geographical regions to explore regional differences. Of a total of 17,491 participants (49.4% male), 22.8% reported depressive symptoms. After adjusting for confounders, participants living in houses that could not prevent cold or heat had a 1.57 (95% CI = 1.45-1.71) times higher prevalence of depressive symptoms than those living in houses that could prevent cold or heat. In the stratified analysis by geographical regions, a significant association was observed in all areas except for Hokkaido, the northernmost area with the coldest climate. In conclusion, perceived indoor cold or heat was associated with an increased prevalence of depressive symptoms among older adults. Further research is expected to investigate the impact of improving the indoor thermal environment, such as by installing insulation, on the prevention of depression.