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 with an aerodynamic diameter ≤ 2.5μm (PM_2.5) as a modifiable risk factor for dementia, but the potential health benefits gained by enacting regulations that reduce PM_2.5 remain unclear.

Objectives: Our aim was to estimate the total effects of hypothetical ambient PM_2.5 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 aged ≥ 55 years at baseline (2010). We estimated the total effects of hypothetical ambient PM_2.5 interventions (achieving annual average standards of 12 μg/m³, 10 μg/m³, and 9 μg/m³) from 2010 to 2019 on the risk of dementia by calculating the difference between the estimated 10-year risk of dementia under a specified hypothetical intervention and the risk under no intervention using the parametric g-formula.

Results: Compared with no intervention, the estimated 10-year risk difference of dementia was -0.54 per 1000 population (95%CI: -1.00, -0.10), -1.36 per 1000 population (95%CI: -2.44, -0.25), -1.92 per 1000 population (95%CI: -3.39, -0.33), with PM_2.5 interventions achieving annual average standards of 12 μg/m³, 10 μg/m³, and 9 μg/m³, respectively.

Discussion: The estimated 10-year risk of dementia decreased if the individual ambient PM_2.5 exposure was reduced due to more stringent PM_2.5 standards in late life compared to the natural course without intervention on ambient PM_2.5 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 PM_2.5 pollution may lower the risk of dementia among UK Biobank participants who would experience more stringent ambient PM_2.5 standards in late life. https://doi.org/10.1289/EHP14723.