Estimating the Effects of Hypothetical Ambient PM2:5 Interventions on the Risk of Dementia Using the Parametric g-Formula in the UK Biobank Cohort

Abstract

BACKGROUND: Emerging evidence identifies ambient particulate matter (PM) with an aerodynamic diameter ≤2:5 lm (PM2:5) as a modifiable risk factor for dementia, but the potential health benefits gained by enacting regulations that reduce PM2:5 remain unclear. OBJECTIVES: Our aim was to estimate the total effects of hypothetical ambient PM2:5 interventions starting in late life on the risk of dementia in a cohort using the parametric g-formula. METHODS: We used data from 291,495 participants in the UK Biobank cohort who were free of dementia and ≥55 y of age at baseline (2010). We estimated the total effects of hypothetical ambient PM2:5 interventions (achieving annual average standards of 12 lg=m3,10lg=m3, and 9 lg=m3) from 2010 to 2019 on the risk of dementia by calculating the difference between the estimated 10-y risk of dementia under a specified hypothetical intervention and the risk under no intervention using the parametric g-formula. RESULTS: In comparison with no intervention, the estimated 10-y risk difference of dementia was −0:54 per 1,000 population [95% confidence interval (CI): −1:00, −0:10], −1:36 per 1,000 population (95% CI: −2:44, −0:25), −1:92 per 1,000 population (95% CI: −3:39, −0:33), with PM2:5 interventions achieving annual average standards of 12 lg=m3,10lg=m3, and 9 lg=m3, respectively. DISCUSSION: The estimated 10-y risk of dementia decreased if the individual ambient PM2:5 exposure was reduced due to more stringent PM2:5 standards in late life in comparison with the natural course without intervention on ambient PM2:5 exposure. Our findings, obtained using the parametric g-formula— a causal inference method that can directly evaluate the impact of hypothetical interventions—suggest that policies reducing ambient PM2:5 pollution may lower the risk of dementia among UK Biobank participants who would experience more stringent ambient PM2:5 standards in late life.