Compound Heatwave and Ozone Pollution Events and the Risk of Neurodegenerative Diseases: A 9-Year Electronic Health Records Cohort Study in China

Abstract Under global warming, compound extreme events combining heatwaves and ozone pollution have become more frequent, but few studies have explored the association of compound events with neurodegenerative diseases (NDD) in the context of population aging. A retrospective cohort study enrolling 587,111 adults aged ≥18 years was conducted using the Yinzhou Regional Health Information Platform (YRHIP) from 2011 to 2019. Compound events were defined as periods when both a heatwave (daily maximum temperature ≥95th percentile for ≥2 consecutive days) and ozone pollution (daily maximum 8-h O3 ≥100 μg/m3 for ≥4 consecutive days) occurred simultaneously. Time-varying Cox proportional hazard models, with threshold effect analysis, stratified analyses, and community-level spatial analyses were performed to quantify health associations. Over a median follow-up of 8.8 years, 2,029 NDD cases were identified. A significant nonlinear association was observed (P_nonlinear = 0.003) such that when annual compound event days were ≥3.667, each one-day increment was associated with a 38% increased NDD risk and a 44% increased Parkinson’s disease (PD) risk. The association was most pronounced among participants over 60 and those with overweight/obesity. While NDD cases clustered in urban regions (Moran’s I = 0.351), rural communities faced higher predicted risk, highlighting the need for joint climate and air quality governance and targeted community health interventions.