Researchers believe that air pollution may be to blame for over 188,000 occurrences of dementia each year in the United States, with wildfires and agricultural activities having the largest effects on a person’s risk of developing Alzheimer’s disease and other types of dementia later in life. The new figures, which were released on Monday in the journal JAMA Network Open, are the most recent to highlight the variety of health concerns that air pollution, as experts have long warned, is a major contributor to.
The current study provides a more detailed look at how some types of air pollution seem to be more strongly associated to dementia than others, despite the fact that studies have already connected poor air quality generally to a range of health issues, including the risk of acquiring dementia. Based on a study of information gathered from a decades-long survey supported by the National Institutes of Health, which followed up with thousands of older persons across the nation every two years regarding their health, their conclusions were reached.
Researchers then merged those data with in-depth air quality modelling to estimate the potential exposure levels of various individuals in the particular places where they lived.
They concentrated on what scientists refer to as PM 2.5 air pollution, a standard for extremely small particles that can be inhaled from the air and are less than 2.5 micrometres broad, or a minuscule portion of the diameter of a human hair. The health impacts of these particles range from coughing and shortness of breath to severe asthma to an increased risk of mortality from heart disease. These particles can come from a variety of sources, including vehicle exhaust and wildfire smoke.
“The environmental community has been working very hard for the past 10 to 15 years to be able to predict exposures,” said Sara Adar, associate chair of epidemiology at the University of Michigan School of Public Health. They drew on a variety of information, such as measurements from the Environmental Protection Agency and specifics on elements in the area that might have an impact on their air quality.
They model every source simultaneously. These many emission sources, such as transportation, agriculture, wildfires, and coal-fired power plants, are all turned off one at a time in the model. They can then compare the levels with and without the emission sources to see the difference, according to Adar.
Even after controlling for a variety of variables that could have produced ambiguous results, such as sex, race and ethnicity, educational attainment, and wealth, their modelling had still identified the greater risk. They could also take into account whether a person had previously lived in an urban or rural location.
Adar recognised they did not have enough data to model every exposure or check for every difference across the course of a person’s life — including where people were born — which would have impacted their conclusions, even though they did have information on where people moved during the survey. Dementia takes a while to manifest. It’s not a case of “oh, you had a bad exposure last week and now you have dementia.” It will probably accumulate throughout a lifetime, according to Adar.
Adar pointed out that their analysis was able to take into account additional types of air pollution that can also be linked to wildfires and agriculture in addition to the direct emissions from these sources. As wildfires burn through communities, various harmful chemicals may be conveyed with the smoke in addition to the smoke itself. Ammonia emissions from sources like manure and fertiliser during farming can also aggravate air pollution.
“Farms will release a lot of ammonia gas, and then in the air with the sunlight and other pollutants out there, they’ll react to make particles, and those particles are what we see, likely toxins for the brain,” said Adar.
In order to address this dementia risk, Adar and Boya Zhang, who is also a researcher at the institution, say they hope their new findings will inspire more focused interventions.
According to the study’s authors, “exposures to air pollution can be modified at the population level, making it a prime target for large-scale prevention efforts,” in contrast to many other major risk factors for dementia (such as hypertension, stroke, and diabetes).