Air pollution, and especially that caused by combustion vehicles, has been associated in recent years with various diseases and increased mortality. In some recent cases, the relationship between poor air quality and mental disorders such as Alzheimer’s has been analyzed.
To clear up any doubts, a team of experts from the Departments of Environmental Health and Epidemiology of the TH Chan School of Public Health in Boston (United States) have reviewed 2,000 studies published worldwide in recent decades on the effects of pollution on human health and have found 51 investigations that provide significant data on dementia and exposure to air with particles smaller than 2.5 microns (PM-2.5), one of the elements usually analyzed in air quality.
The authors of this review study of previously published research conclude that there is evidence of this relationship and that, therefore, the competent bodies and authorities should take this data into account when reviewing regulations and ensuring the improvement of air quality. .
One of the significant data from the study, in this sense, is that the risk of suffering from some type of dementia increases even with levels of contamination that many of the current regulations consider legal. The results of this review study have been published in The British Medical Journal (BMJ), which also includes in its April 5, 2023 issue, an editorial highlighting the value of these data and the need to transfer their conclusions to national and international regulations.
The TH Chan School of Public Health highlights that the now-published study “is the first systematic review and meta-analysis to use the new Robins-E study analysis tool, Risk of bias in non-randomized exposure studies, which reduces technical errors.” and statistics, as well as improving detail in analyzes of environmental health effects.It is also the first to include newer studies that used “active case finding,” a method that involved detection of entire study populations followed by a in-person screening for dementia among people who did not have dementia at baseline, highlights the authors’ medical school.
More than 57 million people worldwide are currently living with dementia, and estimates suggest the number will rise to 153 million by 2050. Up to 40% of these cases are thought to be related to potentially modifiable risk factors, such as exposure to air pollutants.
Mark Weisskopf, Elissa Wilker, and Marwa Osman, co-authors of the new study, reviewed more than 2,000 studies and identified 51 that tested an association between air pollution and clinical dementia, all published within the past 10 years.
These studies were assessed for bias using Robins-E, and 16 of them met the criteria for meta-analysis. Most of the research was on PM-2.5, with nitrogen dioxide and nitrogen oxide being the next most common pollutants studied. Of the studies used in the meta-analysis, nine used active case verification.
“The researchers found consistent evidence of an association between PM-2.5 and dementia, even when annual exposures were less than the US Environment Agency’s current annual standard (12 micrograms per cubic meter of air (μg /m 3 ).
In particular, among the most advanced studies, the researchers found a 17% increase in the risk of developing dementia for every 2 μg/m 3 increase in average annual exposure to PM-2.5.
They also found evidence suggesting associations between dementia and nitrogen oxide (5% increase in risk for every 10 μg/m 3 increase in annual exposure) and nitrogen dioxide (2% increase in risk for every 10 μg/m 3 increase in annual exposure), although the data was more limited.
The researchers noted 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 could be substantial.
“Given the enormous number of dementia cases, the identification of actionable modifiable risk factors to reduce the burden of disease would have tremendous personal and societal impact,” explains Mark Weisskopf. “Exposure to PM-2.5 and other air pollutants is modifiable to some extent by personal behaviors, but more importantly, through regulation.”
