A reduction in fine particulate matter and nitrogen dioxide over a decade is associated with a 20% lower risk of dementia in older women.
Improvement in air quality over ten years was linked to decreased dementia risk, showing hazard ratios of 0.80 for both fine particulate matter and nitrogen dioxide.
A significant association exists between higher baseline levels of fine particulate matter and an increased risk of dementia.
The lower dementia risk linked to improved air quality persisted even after accounting for recent exposure.
The findings indicate that long-term air quality improvements in late life may contribute to reduced dementia risk, regardless of age, education, or cardiovascular factors.
Simplified
Late-life is a risk factor for brain aging, but it remains unknown if improved air quality (AQ) lowers dementia risk. We studied a geographically diverse cohort of older women dementia free at baseline in 2008 to 2012 (= 2,239, aged 74 to 92). Incident dementia was centrally adjudicated annually. Yearly mean concentrations of fine particulate matter (PM) and nitrogen dioxide (NO) were estimated using regionalized national universal kriging models and averaged over the 3-y period before baseline (recent exposure) and 10 y earlier (remote exposure). Reduction from remote to recent exposures was used as the indicator of improved AQ. Cox proportional hazard ratios (HRs) for dementia risk associated with AQ measures were estimated, adjusting for sociodemographic, lifestyle, and clinical characteristics. We identified 398 dementia cases during follow up (median = 6.1 y). PMand NOreduced significantly over the 10 y before baseline. Larger AQ improvement was associated with reduced dementia risks (HR0.80 per 1.78 μg/m, 95% CI 0.71-0.91; HR0.80 per 3.91 parts per billion, 95% CI 0.71-0.90), equivalent to the lower risk observed in women 2.4 y younger at baseline. Higher PMat baseline was associated with higher dementia risk (HR1.16 per 2.90 μg/m, 95% CI 0.98-1.38), but the lower dementia risk associated with improved AQ remained after further adjusting for recent exposure. The observed associations did not substantially differ by age, education, geographic region, Apolipoprotein E e4 genotypes, or cardiovascular risk factors. Long-term AQ improvement in late life was associated with lower dementia risk in older women. n2.5 2 2.5 2PM2.5NO2 2.5PM2.5 3 3
Key numbers
20%
Decrease in dementia risk
Associated with each IQR increment of improved AQ in PM.
13.3 to 10.5 μg/m
PM reduction
Average PM levels before and after the study period.
0.80 per 1.78 μg/m
Dementia risk HR
Hazard ratio for dementia risk associated with AQ improvement.
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