Risk of Dementia Increases with Air Pollution

A recent meta-analysis from the Harvard T.H. Chan School of Public Health suggests that exposure to fine particulate air pollutants (PM2.5) may raise the chance of dementia. “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,” said lead author Marc Weisskopf, Cecil K., and Philip Drinker Professor of Environmental Epidemiology and Physiology. “Our findings support the public health importance of such a measure.”

The research is the first systematic review and meta-analysis to make use of the brand-new Risk of Bias In Non-Randomized Studies of Exposure (ROBINS-E) tool, which goes into greater detail than other assessment methods about bias in environmental studies. It is also the first to include more recent studies that made use of the “active case ascertainment” technique, which involved screening the complete study populations before evaluating those who were dementia-free at baseline in person for dementia.

The BMJ will publicize the research.

There are presently more than 57 million dementia sufferers in the world, and by 2050, that number is predicted to rise to 153 million. According to estimates, up to 40% of these instances may have modifiable risk factors, like exposure to air pollutants.

Weisskopf and his co-authors, Marwa Osman, a doctoral student in the Biological Science in Public Health program, and Elissa Wilker, a researcher in the Harvard Chan-NIEHS Center for Environmental Health, searched more than 2,000 studies and found 51 that examined a connection between ambient air pollution and clinical dementia. These studies were all published within the last ten years.

16 of those studies fulfilled the requirements for the meta-analysis after being evaluated for bias using ROBINS-E. The second and third most frequent pollutants examined after PM2.5 were nitrogen dioxide and nitrogen oxide. Nine of the papers that were incorporated into the meta-analysis did active case ascertainment.

Even when yearly exposure was lower than the current EPA annual standard of 12 micrograms per cubic meter of air (g/m3), the researchers discovered consistent evidence of an association between PM2.5 and dementia. The researchers discovered a 17% rise in risk for dementia for every 2 g/m3 increase in average annual exposure to PM2.5, specifically among the studies using active case ascertainment.

Despite the fact that the data was more sparse, they also discovered evidence indicating links between dementia and nitrogen oxide (5% increase in risk for every 10 g/m3 increase in annual exposure) and nitrogen dioxide (2% increase in risk for every 10 g/m3 increase in annual exposure).

The researchers pointed out that other risk variables, like education and smoking, have larger estimated associations with dementia risk than air pollution. However, given how many individuals are exposed to air pollution, there may be significant health effects at the population level.

“Given the massive numbers of dementia cases, identifying actionable modifiable risk factors to reduce the burden of disease would have tremendous personal and societal impact,” Weisskopf said. “Exposure to PM2.5 and other air pollutants is modifiable to some extent by personal behaviors—but more importantly through regulation.”

Source Link