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

## TL;DR

The study found that long-term exposure to PM2.5 pollution may increase dementia risk in Australian older adults, particularly in females.

## Contribution

This study is novel in identifying sex-specific effects of PM2.5 exposure on dementia risk in a low-pollution setting.

## Key findings

- Females exposed to PM2.5 above 10 µg/m³ had a 2.7-fold higher dementia risk compared to those below 5 µg/m³.
- PM2.5 exposure showed a threshold effect, with increased dementia risk at levels above 10 µg/m³.
- Males did not show a significant association between PM2.5 exposure and dementia risk.

## Abstract

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.

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.

Overall associations were null, but with a trend for increased risk at exposures >10 versus ≤5 µg/m3. In subgroup analyses, positive associations were observed among females, with larger effect estimates at exposure >10 µg/m3, whereas associations remained null among males. No differences were observed across APOE genotypes or age groups.

Findings suggest a threshold of >10 µg/m3 and heightened susceptibility in females. Further research in low‐exposure settings is warranted.

Threshold effect: Although not statistically significant in the overall population, exposure > 10 µg/m3 was associated with increased dementia risk (HR 1.50; 95% CI: 0.97 to 2.31).
Sex difference: Females showed a 7% higher dementia risk per 1 µg/m3 increase (HR 1.07; 95% CI: 1.01 to 1.14); no association was observed in males (HR 1.00; 95% CI: 0.95 to 1.07).
Female vulnerability: Females exposed to >10 µg/m3 had a 2.7‐fold higher risk (HR 2.71; 95% CI: 1.55 to 4.74) compared with ≤5 µg/m3.

Threshold effect: Although not statistically significant in the overall population, exposure > 10 µg/m3 was associated with increased dementia risk (HR 1.50; 95% CI: 0.97 to 2.31).

Sex difference: Females showed a 7% higher dementia risk per 1 µg/m3 increase (HR 1.07; 95% CI: 1.01 to 1.14); no association was observed in males (HR 1.00; 95% CI: 0.95 to 1.07).

Female vulnerability: Females exposed to >10 µg/m3 had a 2.7‐fold higher risk (HR 2.71; 95% CI: 1.55 to 4.74) compared with ≤5 µg/m3.