No Evidence Stroke, Hypertension Mediates Link Between Air Pollution and Dementia

Hypertension and stroke do not mediate or modify the association between exposure to fine particulate matter air pollution (PM_2.5) with incident dementia, according to study results published online in JAMA Network Open.

“Although we hypothesized that hypertension and stroke would mediate or modify associations of PM_2.5 with dementia, it is plausible that the association of air pollution with cognition may be mediated through other pathways,” wrote corresponding author Boya Zhang, PhD, of the University of Michigan School of Public Health, Ann Arbor, Michigan, and study coauthors.

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Researchers used causal mediation modeling to quantify the degree to which hypertension and stroke affected the link between PM_2.5 and incident dementia. The nationally representative cohort study included 27,857 people aged 50 years and older in the United States. Over an average follow-up of 10.2 years, 4105 developed dementia. 

Among participants who developed dementia, 53.7% had a hypertension history at baseline and 9.4% were diagnosed with hypertension during follow up. Meanwhile, 9.2% had a stroke history at baseline and 16.4% experienced stroke over follow-up.

Living in areas with higher levels of PM_2.5 was not associated with increased risk of incident dementia in fully adjusted models, researchers reported. The study did find positive associations between prevalent stroke (1.67 hazard ratio) and hypertension (1.15 hazard ratio) with incident dementia compared with no stroke or hypertension during follow-up. However, analysis revealed no statistically significant association of PM_2.5 with stroke and no association of PM_2.5 with hypertension.

“As a result, additional investigation of the pathways underlying the association of air pollution with dementia is needed to understand disease etiology and identify populations who might benefit most from pollution reduction strategies,” researchers advised.

Reference

Zhang B, Langa KM, Weuve J, et al. Hypertension and stroke as mediators of air pollution exposure and incident dementia. JAMA Netw Open. 2023;6(9):e2333470. doi: 10.1001/jamanetworkopen.2023.33470