Long-term particulate matter 2.5 exposure and dementia: a systematic review and meta-analysis.

OBJECTIVES

This study aimed to analyse the existing evidence on the association between particulate matter 2.5 (PM) and dementia, including two of its subtypes, namely, Alzheimer's disease (AD) and vascular dementia (VaD).

STUDY DESIGN

This was a systematic review and meta-analysis.

METHODS

The PubMed, EMBASE, Cochrane and Web of Science databases were comprehensively searched for articles published between January 1900 and June 2022. All cohort studies that reported the influence of long-term exposure to PM on dementia, together with its subtypes, in adults aged ≥40 years, without any regional restriction were included. A random effects model was used to pool the hazard ratios (HRs) of PM for dementia, AD and VaD. Funnel plots, sensitivity analyses and subgroup analyses were performed to test publication bias and result stability. In addition, an explanation for the heterogeneity of the results was suggested.

RESULTS

In total, 20 articles were selected for review; 18 included results on the long-term effects of PM on dementia, 13 on AD, and eight on VaD. Three group meta-analyses were performed to obtain the HRs and 95% confidence intervals (CIs). The pooled HRs were 1.40 (95% CI 1.23, 1.60) for dementia, 1.47 (95% CI 1.22, 1.78) for AD and 2.00 (95% CI 1.30, 3.08) for VaD per 10.0 μg/m PM increase.

CONCLUSIONS

Long-term exposure to PM may increase the risk of dementia, including AD and VaD. These results highlight the need for further study on the detrimental impact of PM and the importance of strategies to mitigate increasing air pollution.