Association of air quality reduction with incident dementia: Effects of natural course and hypothetical air pollutant interventions using g‐computation

Abstract

AbstractBackgroundThe benefits of air quality improvement on the burden of neurological disorders could be substantial given the emerging evidence regarding the role of air pollution on dementia incidence. However, none evidence exists about the impact of air pollution reduction on incidence of dementia. The aim of this study is to quantify how observed reduction in PM2.5 concentration leads to dementia‐incidence benefits and simulate the benefits of hypothetical air quality improvement interventions on the reduction of dementia incidence.MethodsAmong the French Three‐City Cohort (12 years of follow‐up), dementia diagnoses were made using DSM‐IV criteria and validated by an adjudication committee. Exposure to PM2.5 was estimated using Land Use Regression models. We performed multi‐level Cox proportional and Aalen additive hazard regression models to assess the effect of observed PM2.5 reduction on dementia risk. Then, we used a parametric g‐computation approach to quantify the effects of various hypothetical interventions to reduce PM2.5 exposure on dementia risk.ResultsAmong 7051 participants (median age: 73), the median PM2.5 reduction between 1990 and 2000, 10 years prior to inclusion, was 12.2 (µg/m3). Such reduction reduced the risk of all‐type of dementia (hazard ratio (HR) 0.85, 95% confidence interval (CI):0.76‐0.95) and Alzheimer's disease (HR 0.83, 95%CI:0.72‐0.94). Approximately 197 less cases of all type of dementia per 100 000 persons and year could be attributed to PM2.5 reduction. Using g‐computation, we quantified the expected number of prevented dementia cases under different hypothetical interventions. For example, for compliance with a hypothetical reduction of more than 13.10 µg/m3 (reduction observed in the city of Montpellier), the rate difference was ‐0.33 (95%CI, −0.51 to −0.15).ConclusionThese findings highlight the possible substantial benefits of reducing air pollution in the prevention of dementia.