Harvard Scientists Reveal That Air Pollution May Increase Risk of Dementia

A comprehensive meta-analysis conducted by researchers at the Harvard T.H. Chan School of Public Health has highlighted the potential link between exposure to fine particulate air pollutants (PM2.5) and an increased risk of dementia. The study supports the public health relevance of the Environmental Protection Agency’s proposed plan to tighten regulations on PM2.5, which is currently under evaluation.

“This research marks a significant stride in furnishing regulators and clinicians with actionable data regarding this highly significant health issue. These findings could prove instrumental for organizations like the Environmental Protection Agency, which is in the process of reviewing limits on PM2.5 exposure,” commented Marc Weisskopf, lead author of the study and the Cecil K. and Philip Drinker Professor of Environmental Epidemiology and Physiology.

The research is notable for being the first systematic review and meta-analysis to utilize the Risk of Bias In Non-Randomized Studies of Exposure (ROBINS-E) tool, which offers a more detailed bias assessment for environmental studies. Furthermore, it includes more recent research that uses an “active case ascertainment” methodology, which involves screening entire study populations and conducting in-person dementia assessments for participants who were dementia-free at the start.

Published in The BMJ, the study sheds light on a growing health crisis; currently, more than 57 million people globally suffer from dementia, a figure projected to rise to 153 million by 2050. Up to 40% of these cases are suspected to be related to modifiable risk factors like exposure to air pollutants.

Weisskopf, along with co-authors Elissa Wilker, a researcher in the Harvard Chan-NIEHS Center for Environmental Health, and doctoral student Marwa Osman, examined over 2,000 studies published in the past decade. These studies assessed the connection between ambient air pollution and clinical dementia. Using the ROBINS-E tool for bias evaluation, they selected 16 studies for the meta-analysis, with a major focus on PM2.5, followed by nitrogen dioxide and nitrogen oxide.

The team found a consistent link between PM2.5 exposure and dementia risk, even when annual exposure was below the current EPA standard of 12 micrograms per cubic meter of air. Among the studies employing active case ascertainment, researchers found a 17% rise in dementia risk for every 2 μg/m3 increase in average annual PM2.5 exposure. Limited data also suggested potential links between dementia and nitrogen oxide and nitrogen dioxide exposure.

While the estimated risk of dementia from air pollution is less than other factors like education and smoking, its wide-scale exposure implies substantial population-level health implications.

Weisskopf emphasized the importance of recognizing and modifying risk factors to decrease the disease’s burden, considering the vast number of dementia cases. He noted, “Exposure to PM2.5 and other air pollutants can be altered to some extent by personal behaviors—but more importantly through regulation.”

The study, funded by Biogen and the National Institutes of Health, was published in The BMJ in April 2023.

I agree to the usage of Google Analytics and related cookies across the TrendMD network. Learn more.
Yes No

Frequently Asked Questions (FAQs) about Air Pollution and Dementia Risk

More about Air Pollution and Dementia Risk

• Harvard T.H. Chan School of Public Health
• Environmental Protection Agency (EPA)
• Study: “Ambient air pollution and clinical dementia: systematic review and meta-analysis”
• National Institutes of Health (NIH)
• Biogen
• The BMJ
• Risk of Bias In Non-Randomized Studies of Exposure (ROBINS-E)