The sex‐specific association between long‐term PM2.5 exposure and incident dementia in community‐dwelling older adults in Australia

Abstract INTRODUCTION Air pollution is linked to dementia, but evidence from low‐exposure settings is limited. We examined sex‐specific associations between long‐term exposure to fine particulate matter ≤2.5 µm in diameter (PM2.5) and dementia risk in older adults living in Australia. METHODS In 16,145 dementia‐free Aspirin in Reducing Events in the Elderly (ASPREE) participants (≥70 years; median follow‐up 10.3 years), Cox models assessed associations between 1‐year mean PM2.5 (continuous and guideline‐based categories) and incident dementia, adjusting for demographic, lifestyle, environmental, and genetic factors. Subgroup analyses by sex, apolipoprotein E genotype ( APOE ), and age were conducted. RESULTS Overall associations were null, but with a trend for increased risk at exposures >10 versus ≤5 µg/m 3 . In subgroup analyses, positive associations were observed among females, with larger effect estimates at exposure >10 µg/m 3 , whereas associations remained null among males. No differences were observed across APOE genotypes or age groups. DISCUSSION Findings suggest a threshold of >10 µg/m 3 and heightened susceptibility in females. Further research in low‐exposure settings is warranted.