Impact of heatwaves on elderly depression symptoms in the context of climate change: the moderating role of community-based care services

The intensification of climate change and global warming has increased the frequency of extreme weather events, such as heatwaves, posing significant health risks to the elderly population. This study employs data from the 2005–2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS) and meteorological station records from mainland China (1974–2019) to examine associations between heatwave exposure and depression symptoms among older adults. Heatwave events are identified using the Wet Bulb Globe Temperature (WBGT) index, and multidimensional heatwave indicators, including daily heatwave magnitude, single heatwave duration, heatwave frequency, cumulative heatwave days, and a heatwave exposure index, are constructed. A fixed-effects model is employed to estimate associations for event-level and cumulative exposure. The moderating role of community-based care services and heterogeneity across demographic groups and regions are also explored. The findings reveal that cumulative heatwave exposure indicators, such as heatwave frequency and cumulative heatwave days, are more consistently associated with higher depression symptoms than event-level indicators, highlighting the cumulative and repetitive stress associated with prolonged exposure. Community-based care services are associated with smaller heatwave-related increases in depressive symptoms, but effects are threshold-sensitive: a greater number of services significantly mitigates risks at lower thresholds yet attenuates and disappears under more extreme heatwaves, when older adults rely more on direct support (e.g., Personal Care Services and Neighborhood-Relation Mediation Services) than on service diversity. Service-specific patterns further indicate that Health Education is protective mainly at lower thresholds, whereas Daily Shopping Services emerges at higher thresholds. Robustness tests confirm the significance of heatwave exposure effects across conventional heatwave thresholds, with diminished significance at very high cut-offs. Heterogeneity analysis shows that individuals aged 85 and older, cohabiting older adults, and residents of North China are more vulnerable to heatwave exposure, with higher risks of psychological distress compared to other groups. This study underscores the need for targeted interventions, including enhanced community-based care services, to reduce heatwave-related mental health risks among vulnerable elderly populations.