Ambient temperature and 24-hour movement behaviors in community-dwelling older adults in Japan: The Kyotango Longevity Cohort Study

Background: Sedentary behavior (SB), physical activity, and sleep duration are 24-hour movement behaviors and key indicators of healthy aging. This study examined the association between daily mean ambient temperature and 24-hour movement behaviors among community-dwelling older adults. Methods: Data were obtained from 769 participants aged ≥ 65 years (mean age 73.5 ± 5.5 years; 59.0% female) in the Kyotango Longevity Cohort Study conducted in Kyotango City, Japan. SB and physical activity were objectively assessed in each participant using a triaxial accelerometer over 7 consecutive days (4,344 valid person-days in total). Associations between daily mean ambient temperature and 24-hour movement behaviors were evaluated using linear mixed-effects models with natural cubic splines. The association between ambient temperature and sleep duration, estimated from sleep diaries or standardized sleep windows when diary data were unavailable, was also examined. Results: Significant non-linear associations were observed between daily mean ambient temperature and all 24-hour movement behaviors (all p < 0.05). SB exhibited a U-shaped pattern, with the predicted minimum at approximately 20.8 °C. By contrast, light-intensity and moderate-to-vigorous-intensity physical activity showed inverted U-shaped associations, peaking at approximately 20.7 °C and 21.1 °C, respectively. Sleep duration remained relatively stable at low-to-moderate ambient temperatures but tended to decline above approximately 22 °C. Conclusions: Ambient temperature is an important environmental factor associated with 24-hour movement behaviors in older adults. These findings underscore the importance of considering thermal conditions when developing strategies to reduce SB, increase physical activity, and maintain appropriate sleep durations in older adults.