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

Yong-Li Zhao; Yi Qu; Ya-Nan Ou; Ya-Ru Zhang; Lan Tan; Jin-Tai Yu

doi:10.1016/j.arr.2021.101504

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

Ageing Res Rev. 2021 Dec:72:101504. doi: 10.1016/j.arr.2021.101504. Epub 2021 Oct 29.

Authors

Yong-Li Zhao¹, Yi Qu¹, Ya-Nan Ou¹, Ya-Ru Zhang², Lan Tan³, Jin-Tai Yu⁴

Affiliations

¹ Department of Neurology, Qingdao Municipal Hospital, Qingdao University, China.
² Department of Neurology and Institute of Neurology, Huashan Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontier Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.
³ Department of Neurology, Qingdao Municipal Hospital, Qingdao University, China. Electronic address: dr.tanlan@163.com.
⁴ Department of Neurology and Institute of Neurology, Huashan Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontier Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China. Electronic address: jintai_yu@fudan.edu.cn.

PMID: 34755643
DOI: 10.1016/j.arr.2021.101504

Abstract

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

Methods: We systematically searched PubMed, EMBASE, Web of Science, and PsychINFO till January 11, 2021 for observational studies. The hazard ratio (HR), relative risk (RR), and odds ratio (OR) with 95% confidence interval (CI) were aggregated using random-effects methods. The quality of evidence for each association was evaluated.

Results: Of the 48,399 publications identified, there were 185 suitable for review across 44 environmental factors. Meta-analyses were performed for 22 factors. With high-to-moderate quality of evidence, risks were suggested in exposure to PM_2.5 (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), road proximity (OR=1.08, 95%CI: 1.04-1.12) and other air pollutions, yet more frequent social contact (HR=0.82, 95%CI: 0.76-0.90) and more greenness (OR=0.97, 95%CI: 0.95-0.995) were protective. With low-to-very low quality, electromagnetic fields, pesticides, SO₂, neighborhood socioeconomic status, and rural living were suggested risks, but more community cultural engagement might be protective. No significant associations were observed in exposure to PM₁₀, NO_x, noise, silicon, community group, and temperature. For the remaining 22 factors, only a descriptive analysis was undertaken as too few studies or lack of information.

Conclusions: This review highlights that air pollutions, especially PM_2.5 and NO₂ play important role in the risk for age-related cognitive impairment and dementia.

Keywords: Cognitive impairment; Dementia; Environment; Meta-analysis; Modifiable factors; Observational studies.

Publication types

Meta-Analysis
Research Support, Non-U.S. Gov't
Systematic Review

MeSH terms

Air Pollutants* / analysis
Air Pollutants* / toxicity
Air Pollution* / analysis
Air Pollution* / statistics & numerical data
Cognitive Dysfunction* / epidemiology
Cognitive Dysfunction* / etiology
Dementia* / epidemiology
Dementia* / etiology
Environmental Exposure / analysis
Environmental Exposure / statistics & numerical data
Humans
Neurodegenerative Diseases*
Particulate Matter / analysis
Particulate Matter / toxicity

Substances

Air Pollutants
Particulate Matter