Environmental factors and risks of cognitive impairment and dementia: a systematic review and meta-analysis


Aging Rev. 2021 October 29; 72: 101504. doi: 10.1016 / j.arr.2021.101504. Online ahead of print.


Background: Dementia is a difficult neurodegenerative disease. This systematic review aimed to summarize the natural, physical and social environmental factors associated with age-related cognitive impairment and dementia.

METHODS: We systematically searched PubMed, EMBASE, Web of Science, and PsychINFO until January 11, 2021 for observational studies. Risk ratio (HR), relative risk (RR), and odds ratio (OR) with a 95% confidence interval (CI) were aggregated using random-effects methods. The quality of the evidence for each combination was assessed.

RESULTS: Of the 48,399 identified publications, 185 were suitable for review on 44 environmental factors. Meta-analyzes were performed for 22 factors. With high to moderate quality evidence, risks have been suggested in PM exposure2.5 (HR = 1.24, 95% CI: 1.17-1.31), NO2 (HR = 1.07, 95% CI: 1.02-1.12), aluminum (OR = 1.35, 95% CI: 1.14-1.59), solvents (OR = 1.14, 95 % CI: 1.07-1.22), proximity to the road (OR = 1.08, 95% CI: 1.04-1.12) and other air pollution, but social contact more frequent (HR = 0.82, 95% CI: 0.76-0.90) and more greenery (OR = 0.97, 95% CI: 0.95-0.995) were protective. With low to very low quality electromagnetic fields, pesticides, SO2, neighborhood socio-economic status and rural life were suggested risks, but more community-based cultural engagement could be protective. No significant association was observed in PM exposureten, NOX, noise, silicon, community group and temperature. For the remaining 22 factors, only a descriptive analysis was undertaken because too few studies or lack of information.

CONCLUSIONS: This review underlines that atmospheric pollution, in particular PM2.5 and no2 play an important role in the risk of age-related cognitive impairment and dementia.

PMID:34755643 | DO I:10.1016 / j.arr.2021.101504

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