Exposure to fine airborne particulate pollutants (PM2.5) may increase the risk of developing dementia, according to a new meta-analysis from the Harvard TH Chan School of Public Health (United States), as published by researchers in the journal The BMJ (1).
“This is a big step in providing regulatory agencies and clinicians with data to understand the state of the literature on this very important health topic,” said Marc Weisskopf, lead author and Cecil K. and Philip Drinker Professor. of Environmental Epidemiology and Physiology–Our findings support the public health importance of such a measure.”
The study is the first systematic review and meta-analysis to use the new tool Risk of Bias In Non-Randomized Studies of Exposure (ROBINS-E), which addresses bias in environmental studies in greater detail than other assessment approaches.
57 million people suffer from dementia worldwide
It is also the first to include more recent studies that used the active case detectiona method that involved the population screening study subjects followed by in-person assessment for dementia among individuals who did not have dementia at baseline.
Currently, more than 57 million people suffer from dementia worldwide, and this number is estimated to increase to 153 million in 2050. It is believed that up to 40% of these cases are related to potentially modifiable risk factors, such as exposure to atmospheric contaminants.
Weisskopf and her co-authors, Elissa Wilker, a researcher at the Harvard Chan Center for Environmental Health-NIEHS, and Marwa Osman, a doctoral student in the Biological Sciences in Public Health program, reviewed more than 2,000 studies and identified 51 that evaluated an association between the Environmental air pollution and clinical dementiaall published in the last 10 years.
Nitrogen dioxide and nitrogen oxide the most commonly studied pollutants
These studies were assessed for bias using ROBINS-E, and 16 of them met the criteria for the meta-analysis. Most of the research concerned PM2.5, with nitrogen dioxide and nitrogen oxide being the next most commonly studied pollutants. Of the studies used in the meta-analysis, nine used active case finding.
The researchers and the researchers found consistent evidence of an association between PM2.5 and dementiaeven when annual exposure was less than EPA’s current annual standard of 12 micrograms per cubic meter of air (micrograms/m3).
In particular, among studies using active case finding, researchers found a 17% increased risk of developing dementia for every 2 micrograms/m3 increase in mean annual PM2.5 exposure. youalso found evidence suggesting associations between PM2.5 and dementia.
Associations Between Dementia and Nitrogen Oxide and Nitrogen Dioxide
They also found evidence suggesting associations between dementia and nitrogen oxide (5% increased risk for every 10 microgram/m3 increase in annual exposure) and nitrogen dioxide (2% increased risk for every 10 microgram /m3 increase in annual exposure), although the data was more limited.
The researchers found that the estimated association of air pollution with dementia risk is less than that of other risk factors, such as education and smoking. However, due to the number of people exposed to air pollution, the health implications at the population level they could be substantial.
“Given the enormous number of dementia cases, the identification of modifiable risk factors to reduce the disease burden would have enormous personal and social impact Weisskopf says. Exposure to PM2.5 and other air pollutants is modifiable to some extent by personal behavior, but the most important thing is regulation“.
References
- (1) Ambient air pollution and clinical dementia: systematic review and meta-analysis. The BMJ.