BACKGROUND: In countries with mild winter climates and inadequate heating, the relationship between housing conditions and health outcomes in winter have not been well studied. The purpose of the present study was to evaluate the relationship between heater type and temperature factors in the bedroom and incidence of the common cold among children in Japan. METHODS: In this prospective cohort study, we distributed baseline questionnaires and temperature loggers in December 2019 and administered follow-up questionnaires in March 2020. We recruited children under the age of 15 years. We performed Poisson regression analysis and logistic regression analysis. RESULTS: Of 297 participants, air conditioners were the most prevalent (n = 105, 35%), followed by gas or kerosene heaters (n = 50, 17%), and floor heaters (n = 31, 10%). Air-conditioners were associated with higher incidence of all events related to the common cold, especially having a fever (adjusted incidence rate ratio (aIRR) = 1.84, 95% confidence interval (CI): 1.41-2.40). Gas or kerosene and floor heaters showed a lower incidence rate of some events related to the common cold, such as school or nursery school absence (aIRR = 0.55, 95% CI: 0.37-0.82 and aIRR = 0.39, 95% CI: 0.23-0.67, respectively). Bedroom temperature did not show a positive association, but children who always felt cold showed a higher incidence of some events related to the common cold. CONCLUSIONS: Our findings imply that the heating approach and modal thermal comfort, such as location of heating appliances, humidity, airflow, and radiant heat, may be more important for the onset of common cold in children than bedroom temperature itself.
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