One, three, or five years of exposure to outdoor particulate matter 2.5 (PM2.5) increased the risk of developing Alzheimer’s disease among healthy elderly people. PM2.5 are inhalable air pollutant particles in diameter of 2.5 micrometers or less, which can be at least 20 times smaller than a human hair. 

Over years of urban development across the world, increased air pollution is also raising the risk of people developing health issues, such as lung and heart diseases. It particularly puts the vulnerable people at risk, including the elderly, children, and those who are living in the areas with a high level of air pollution.   

Only in recent years, there have been discussions about the impact of air pollution on the onset of neurodegenerative diseases. Loss of nerve cells in the brain leads to neurodegenerative disease, including Alzheimer’s and Parkinson’s disease. Few studies investigated the relations between air pollution and onset of Alzheimer’s among healthy elderly people.  

Among all the common air pollutants, PM2.5 is the main one that leads to air pollution-related health issues globally. The major sources of outdoor PM2.5 are emissions from gasoline, diesel fuel, oil processing, or wood burning. 

Researchers from the Emory University in Atlanta in the United States looked into the relation between 1, 3, or 5 years of outdoor PM2.5 exposure and the risk of developing Alzheimer’s among the healthy elderly.

They analysed 1,113 individuals’ data collected between 2016-2020 from the Emory Healthy Brain Study (EHBS) that focuses on cognitive health of older adults. The individuals included in the study were from the Atlanta metropolitan area where the population density is the highest, compared with all other areas in its state of Georgia.

To calculate different years of outdoor PM2.5 exposure, they collected the data from the Socioeconomic Data and Application Center (SEDAC) air quality dataset that is freely accessible to the public. 

To evaluate the signs of Alzheimer’s development, the researchers measured biological markers in the cerebrospinal fluid that is inside and surrounds the brain and spinal cord. These biological markers, including amyloid-beta 42, are validated protein markers in the clinic that can indicate the brain structure changes due to Alzheimer’s. Patients with Alzheimer’s show a lower level of amyloid-beta 42 in the cerebrospinal fluid than healthy individuals. 

The researchers found that the older adults who were exposed to outdoor PM2.5 for 1 or 3 years showed significantly lower levels of amyloid-beta 42 in the cerebrospinal fluid. They also found that 1-, 3-, or 5-year exposure of outdoor PM2.5 increased the possibility of individuals developing Alzheimer’s by 20% to 23%. 

These findings suggest that long-term exposure of outdoor PM2.5 increases the risk of Alzheimer’s among the healthy elderly, via increasing the amount of amyloid-beta 42 accumulation in the brain. In the future, scientists should consider identifying the specific components of outdoor PM2.5 that are toxic to the central nervous system in the brain. They should also consider evaluating which components increase the risk of Alzheimer’s onset. 

This study was published in Environmental Health Perspectives. Image credit: Pixabay

Got any comments or questions on this article? Please reach out to me on LinkedIn, X (Twitter), or the CONTACT ME page, I would love to hear thoughts from you. 

Share this article: