A new study review revealed that exposure to particulate air pollutants might lead to an increased risk of dementia, even with pollution levels below EPA standards.
The study, a Harvard T.H. Chan School of Public Health meta-analysis, scanned more than 2,000 papers for associations between ambient pollutants and clinical dementia.
Data revealed that long-term exposure to PM2.5 particulate matter (particles smaller than 2.5 microns in diameter) at levels below the Environmental Protection Agency (EPA) standards leads to increased dementia risk.
The meta-analysis is the first systematic review to use the new Risk of Bias In Non-Randomized Studies of Exposure (ROBINS-E) approach, which more thoroughly addresses bias issues in environmental studies than other assessment tools.
According to the report, most of the reviewed studies “were at high risk of bias,” although bias proved negligible in effect in many cases.
The meta-analysis is also the first to include newer studies that used “active case ascertainment,” a method that involves in-person evaluation for dementia among individuals who did not have dementia at baseline as a follow-up to the screening of entire study populations.
The studies that rely on active case ascertainment indicate a 17 percent increase in risk for developing dementia for every 2 μg/m³ increase in average annual exposure to PM2.5.
“This is a big step in providing actionable data for regulatory agencies and clinicians in terms of making sense of the state of the literature on this hugely important health topic. The results can be used by organizations like the Environmental Protection Agency, which is currently considering strengthening limits on PM2.5 exposure,” lead authors Marc Weisskopf, Cecil K., and Philip Drinker told The Harvard Gazette.
The researchers remarked that the increased risk of dementia caused by PM2.5 air pollution is significantly smaller than that of other factors, mentioning smoking and education specifically. However, the population-wide health implications could be substantial because everyone is exposed to air pollution to some degree.
“Studies that evaluate critical periods of exposure and pollutants other than PM2.5, and studies that actively assess all participants for outcomes are needed,” the study concludes. “Nonetheless, our results can provide current best estimates for use in [the] burden of disease and regulatory setting efforts.”
The current EPA standard for PM2.5 particles is set at 12 µg/m³, well below the limits of the UK and the European Union set at (20 µg/m³).
Estimates expect the number of people suffering from dementia to increase from the reported 57 million in 2019 to over 150 million by 2050. This trend can mainly be attributed to population aging, although 40 percent of these cases are thought to be linked to modifiable factors such as air pollution.
