Unveiling complexity in blue spaces and life expectancy

Although growing evidence supports the positive impact of blue spaces on human health, research on their association with life expectancy remains limited. This study examines the association between coastal and inland waters and life expectancy across 66,263 census tracts in the United States, incorporating socioeconomic, demographic, and geographic factors through multiple linear and multi-level regression as well as spatial regression models, supplemented by sensitivity analyses. Our findings indicate that proximity to coastal waters is positively associated with life expectancy, whereas proximity to inland waters is negatively associated. We used the mutual information model to identify key factors contributing to these differences. Through a comparative analysis of coastal and inland water environments, we found that longer life expectancy near coastal waters may be linked to more favorable environmental and socioeconomic conditions. These include milder temperatures, better air quality, enhanced recreational opportunities, improved transportation, lower drought susceptibility, and higher income levels. The urban–rural analysis further reveals that proximity to coastal waters is positively associated with life expectancy in both settings, whereas inland waters show differing associations, being negative in urban areas and positive in rural areas. In addition to examining these blue space patterns, this study also considers broader socioeconomic and environmental factors related to life expectancy. These findings highlight the importance of integrating blue spaces and other key environmental and socioeconomic factors into urban planning, residential development, and healthcare environment design to improve life expectancy and health equity.