Long-Term Risk of Chronic Disease from Cold Indoor Environments: A 10-Year Cohort Study

¹ Faculty of Environmental Engineering, The University of Kitakyushu, Kitakyushu, Fukuoka, Japan
² Nikken Sekkei Research Institute, Tokyo, Japan
³ Department of Architecture and Building Engineering, School of Environment and Society, Institute of Science Tokyo, Tokyo, Japan
⁴ Institute for Built Environment and Carbon Neutral for SDGs (IBECs), Tokyo, Japan

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Abstract. Cold exposure is a well-established environmental risk factor for adverse health outcomes; however, evidence regarding the long-term health effects of sustained exposure to cold indoor environments remains limited. This study examined the association between indoor thermal conditions and the long-term incidence of chronic diseases using a 10-year prospective cohort design. The analytical sample comprised 744 community-dwelling adults living in Yusuhara Town, a rural mountainous municipality in western Japan characterized by cold winter conditions and predominantly detached housing. Baseline questionnaire surveys were conducted in 2013, followed by a second survey incorporating objective indoor temperature measurements in 2019 and a third follow-up survey in 2023. Indoor air temperature was measured in frequently occupied living spaces during early winter 2019. Because continuous long-term monitoring was not feasible, these measurements were used as a proxy for long-term residential thermal exposure, assuming relative stability of housing characteristics and heating practices. Incident cases of hypertension, cardiovascular disease, and dyslipidemia were identified based on self-reported physician diagnoses during follow-up. Missing data were handled using multiple imputation, and propensity score analysis was applied to control for potential confounding factors, including demographic, lifestyle, and socioeconomic variables. The results demonstrated that participants exposed to lower indoor temperatures or living in thermally poor dwellings had significantly higher odds of developing chronic diseases over the 10-year period. Individuals residing in inadequately insulated homes exhibited a 2.46-fold higher odds of incident hypertension. In addition, participants with low thermal evaluation scores based on questionnaire assessments had a 2.30-fold increased odds of cardiovascular disease and a 1.83-fold higher odds of dyslipidemia compared with those living in thermally favorable environments. These findings suggest that sustained exposure to cold indoor environments may substantially elevate the long-term risk of chronic disease. Improving residential thermal conditions—particularly through enhanced insulation across the entire dwelling, including unheated spaces—may represent an important complementary strategy for long-term health promotion.