Effect of indoor air quality on the association of long-term exposure to low-level air pollutants with cognition in older adults.

Background: How indoor air quality affects the temporal associations of long-term exposure to low-level air pollutants with cognition remains unclear.

Methods: This cohort study (2011-2019) included 517 non-demented older adults at baseline with four repeated cognitive assessments. The time-varying exposure to PM, PM, NO, SO, CO, and O was estimated for each participant from 1994 to 2019. Indoor air quality was determined by ventilation status and daily indoor time. Generalized linear mixed models were used to analyze the association of air pollutants, indoor air quality, and cognition adjusting for important covariates.

Results: Over time, per 2.97 μg/m (i.e., an interquartile range) increment of PM was associated with the poor performance of memory (Z score of a cognitive test, βˆ:-0.14), attention (βˆ:-0.13), and executive function (βˆ:-0.20). Similarly, per 2.05 μg/m increase in PM was associated with poor global cognition [adjusted odds ratio (aOR): 1.48, βˆ:-0.28], attention (βˆ:-0.07), and verbal fluency (βˆ:-0.09); per 4.94 μg/m increase in PM was associated with poor global cognition (aOR: 1.78; βˆ:-0.37). In contrast, per 2.74 ppb increase in O was associated with better global cognition (βˆ:0.36 to 0.47). These associations became more evident in participants with poor ventilation or short daily indoor time (<12.5 h/day). For global cognition, the exposure to a 10-μg/m increment in PM, PM, and PM corresponded to 1.4, 5.8, and 2.8 years of aging, respectively.

Conclusion: This study demonstrated how indoor air quality in areas using clean fuels differentially affected the associations of long-term exposure to low-level air pollutants with cognition. Tightening air quality standards may help prevent dementia.