Environmental factors and risks of cognitive impairment and dementia: A systematic review and meta- analysis
Abstract
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. Environmental factors and risks of cognitive impairment and dementia: A systematic review and meta-analysis. Ageing Res Rev. 2021 Oct 29;72:101504. doi: 10.1016/j.arr.2021.101504. Highlights • Air pollution, tobacco smoke and pesticides could elevate the risks of dementia. • Exposure to electromagnetic fields was found positive associated with dementia. • Solvents and aluminum were found hazard for dementia, while silicon might be benefit. • Living in rural area and more deprived neighborhood were adverse for dementia. • Residential greenness and social contacts were proposed as beneficial factors. 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 PM2.5 (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 pollution, 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, NOx, 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 pollution, especially PM2.5 and NO2 play important role in the risk for age-related cognitive impairment and dementia. pubmed.ncbi.nlm.nih.gov Excerpts 3.2.2. Electromagnetic fields (EMFs) From 27 studies, we found electromagnetic fields exposure was associated with dementia (OR=1.27, 95% CI: 1.13–1.43, I2 =76.7%, S- grade, Fig. 3) with low-quality evidence, and among them, 11 were cohort studies and 16 were case-control studies (Appendix Figure 1.7). The result was robust via sensitivity analysis (Appendix Figure 3.8). Moreover, 23 studies focused on the outcome of AD, and 4 focused on VaD. Subgroup analysis displayed a significant association between EMFs with AD, but not with VaD (Fig. 3). In addition, the correlation with AD was observed in both females (OR=2.33, 95% CI: 1.19–4.57, I2 =49.8%) and male (OR=1.51, 95% CI: 1.21–1.89, I2 =46.4%, Appendix Figure 1.7.4). EMFs Exposure was mostly from occupation according to job- exposure information, and living next to the power line in life was not linked to dementia or AD (Fig. 3).
AI evidence extraction
Main findings
This systematic review and meta-analysis of observational studies reports that electromagnetic field (EMF) exposure was positively associated with dementia overall (reported OR=1.27, 95% CI: 1.13–1.43) with low-quality evidence and substantial heterogeneity (I2=76.7%). Subgroup analyses reported a significant association with Alzheimer’s disease but not with vascular dementia. The authors note EMF exposure was mostly occupational based on job-exposure information, and living next to power lines was not linked to dementia or AD in their analyses.
Outcomes measured
- Dementia
- Alzheimer's disease (AD)
- Vascular dementia (VaD)
- Age-related cognitive impairment
Limitations
- Evidence for EMF association was rated low-to-very low quality.
- Included studies were observational (cohort and case-control), which are subject to confounding and bias.
- Substantial heterogeneity was reported for the EMF-dementia association (I2=76.7%).
- Exposure assessment was largely based on occupational/job-exposure information; residential power-line proximity findings differed.
Suggested hubs
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occupational-exposure
(0.86) EMF exposure was mostly from occupation according to job-exposure information.
-
power-lines
(0.62) Residential exposure via living next to power lines was specifically discussed.
View raw extracted JSON
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"summary": "This 2021 systematic review and meta-analysis synthesized observational evidence on environmental factors and dementia risk. For electromagnetic fields, the authors report a positive association with dementia overall, but rate the evidence as low quality and note substantial heterogeneity. They report an association with Alzheimer’s disease but not vascular dementia, and indicate occupational EMF exposure predominated while residential power-line proximity was not linked to dementia or AD.",
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"The EMF evidence was graded as low quality and showed high heterogeneity (I2=76.7%).",
"Subgroup analyses reported an association between EMFs and Alzheimer’s disease but not vascular dementia.",
"Reported sex-stratified analyses found associations with AD in both females and males.",
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"facebook": "A 2021 systematic review and meta-analysis of observational studies examined many environmental factors for dementia risk. For electromagnetic fields (EMFs), it reported a positive association with dementia overall, but rated the evidence as low quality and noted substantial heterogeneity. The association was reported for Alzheimer’s disease but not vascular dementia, and exposure was mostly occupational; living near power lines was not linked to dementia or AD in this review.",
"linkedin": "Systematic review/meta-analysis (2021) on environmental factors and dementia: EMF exposure was reported as positively associated with dementia overall, though evidence was graded low quality with substantial heterogeneity. Subgroup analyses reported an association with Alzheimer’s disease but not vascular dementia; exposure was largely occupational, and power-line proximity was not linked to dementia/AD in the review."
}
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AI can be wrong. Always verify against the paper.
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