The role of cardiovascular disease in the relationship between air pollution and incident dementia: a population-based cohort study

Abstract

Background Evidence suggests a link between air pollution and dementia. Cardiovascular disease (CVD) may be a potential determinant of dementia. This motivated us to quantify the contribution of CVD to the association between air pollution and dementia. Methods A cohort of Canadian-born residents of Ontario, who participated in the 1996–2003 Canadian Community Health Surveys, was followed through 2013 or until dementia diagnosis. Exposure to nitrogen dioxide (NO2) and fine particulate matter (PM2.5) was estimated with a 3-year average and 5-year lag before dementia diagnosis. Incident CVD was evaluated as a mediator. We used multi-level Cox proportional and Aalen additive hazard regression models, adjusting for individual- and neighbourhood-level risk factors to estimate associations with NO2 and PM2.5. We estimated the total, direct and indirect effects of air pollution on dementia through cardiovascular disease. Results This study included 34 391 older adults. At baseline, the mean age of this cohort was 59 years. The risk of dementia was moderately higher among those more exposed to NO2 (hazard ratio (HR) 1.10, 95% confidence interval (CI) 0.99–1.19; and 100 additional cases per 100 000 [standard error (SE) <100x10-5]) and PM2.5 [(HR 1.29, 95% CI 0.99–1.64; 200 additional cases per 100 000] [SE 100x10-5]) after adjusting for covariates; however, these estimates are imprecise. A greater proportion of the relationship between PM2.5 and dementia was mediated through CVD than NO2 for both scales. Conclusions These results suggest some of the association between air pollution and dementia is mediated through CVD, indicating that improving cardiovascular health may prevent dementia in areas with higher exposure to air pollution.

Exposure to air pollution and cognitive impairment risk: a meta-analysis of longitudinal cohort studies with dose-response analysis

“…Based on these findings, many studies have evaluated the association between air pollution and cognitive impairment. Specifically, for PM2.5 exposure, a positive association was found in four studies [17][18][19], whereas no significant association was shown in other studies [20][21][22][23][24][25]. For NO2/NOx exposure, although the risk of cognitive impairment was illustrated in two studies [17,18], the link was not manifested in…”

“…other studies [20,21,25,26]. For O3 exposure, one study [17] revealed an inverse relationship with cognitive impairment, while another study [20] found a positive relationship with cognitive impairment.…”

“…Ultimately, ten articles [17][18][19][20][21][22][23][24][25][26], including 11 studies on PM2.5, 7 studies on NO2/NOx and 4 studies on O3, were satisfied the inclusion criteria and were enrolled in this meta-analysis. Eight articles [18,[21][22][23][24][25][26] were population-based studies and two articles [19,20] were hospital-based studies.…”

“…Ultimately, ten articles [17][18][19][20][21][22][23][24][25][26], including 11 studies on PM2.5, 7 studies on NO2/NOx and 4 studies on O3, were satisfied the inclusion criteria and were enrolled in this meta-analysis. Eight articles [18,[21][22][23][24][25][26] were population-based studies and two articles [19,20] were hospital-based studies. The duration of follow-up ranged from 4 to 18 years, with three articles [17,22,23] following equal to or less than 10 years and seven articles [18][19][20][21][24][25][26]] more than 10 years.…”

“…Eight articles [18,[21][22][23][24][25][26] were population-based studies and two articles [19,20] were hospital-based studies. The duration of follow-up ranged from 4 to 18 years, with three articles [17,22,23] following equal to or less than 10 years and seven articles [18][19][20][21][24][25][26]] more than 10 years. Concerning the study areas, four articles [17,20,24,26] were performed in Europe, five articles [18,19,21,23,25] in North America and one article [22] in Asia.…”