Air Pollution and Alzheimer’s Disease: A Systematic Review and Meta-Analysis

Abstract

Background: Ambient air pollution has been associated with Alzheimer’s disease (AD) in the elderly. However, its effects on AD have not been meta-analyzed comprehensively. Objective: We conducted a systematic review and meta-analysis to assess the associations between air pollution and AD incidence. Methods: We searched PubMed and Web of Science for indexed publications up to March 2020. Odds risk (OR) and confidence intervals (CI) were estimated for particulate matter (PM)10 (PM10), PM2.5, ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). The subgroup analysis was conducted based on the pollution levels. Results: Nine studies were included in the meta-analysis and review. The OR per 10μg/m3 increase of PM2.5 was 1.95 (95% CI: 0.88–4.30). The corresponding values per 10μg/m3 increment of other pollutants were 1.03 (95% CI: 0.68–1.57) for O3, 1.00 (95% CI: 0.89–1.13) for NO2, and 0.95 (95% CI: 0.91–0.99) for PM10 (only one study), respectively. Overall OR of the five air pollutants above with AD was 1.32 (95% CI: 1.09–1.61), suggesting a positive association between ambient air pollution and AD incidence. The sub-analysis indicated that the OR (2.20) in heavily polluted regions was notably higher than that in lightly polluted regions (1.06). Although AD risk rate data related to SO2 or CO exposure are still limited, the epidemiologic and toxicological evidence indicated that higher concentration of SO2 or CO exposure increased risks of dementia, implying that SO2 or CO might have a potential impact on AD. Conclusion: Air pollution exposure may exacerbate AD development.

The Effects of Chronic Exposure to Ambient Traffic-Related Air Pollution on Alzheimer’s Disease Phenotypes in Wildtype and Genetically Predisposed Male and Female Rats

“…Epidemiological data indicate a strong association between traffic-related air pollution (TRAP) and increased risk of age-related dementia, including Alzheimer’s disease (AD) ( Fu and Yung 2020 ; Peters et al. 2019 ).…”

Exploration of the Global Burden of Dementia Attributable to PM2.5: What Do We Know Based on Current Evidence?

“…Both epidemiologic and animal toxicological studies have begun to address the above limitations, while recent studies have extended that range of PM2.5 exposures included in the epidemiological evidence base (Jung et al, 2015, Qiu et al, 2019). Yet additional studies from more heavily polluted regions are still required (Fu and Yung, 2020).…”

Long-term air pollution exposure and incident dementia in American elderly population: a national cohort study (2000-2018)

“…Among them, 5 of 6 showed a positive association between increased exposure to PM2.5 and dementia or AD; 4 of 4 showed an association between NO2 and dementia or AD, while 1 of 3 did so for ozone (O3). Fu and Yung (2020) 5 published a review and meta-analysis of AD and air pollution, and found a 2-fold excess risk of AD for a 10 µg/m 3 increase of PM2.5 among 6 studies, and no increased risk for NO2 in four studies, nor for O3 in three studies. There have been several longitudinal studies since these reviews, with the majority finding positive associations between air pollutants and either dementia or AD [6][7][8][9][10][11][12][13][14] .…”

“…5. A cohort study conducted in Ontario, Canada by 22 simultaneously accessed the effects of PM2.5, NO2, and O3 on dementia risks, and they also found significant associations with PM2.5 and NO2, but not O3.…”