Exposure to Air Pollution Late in Life Linked To Increased Risk of Alzheimer’s Disease: Study

Older adults who are exposed to air pollution may experience brain shrinkage consistent with Alzheimer’s disease, even when the exposure is at levels that are generally considered “safe”, according to the findings of a new study that highlights the importance of taking steps to modify the risk factor.

A report published this month in the medical journal Neurology indicates that individuals over the age of 70 who live in areas with higher levels of air pollution have increased gray matter atrophy in their brain, which is similar to what is found among individuals with Alzheimer’s disease.

As a result of the findings, researchers recommend that older individuals living in those areas make concerted efforts to reduce their exposure risk, by monitoring air quality and staying in doors when levels of pollution are high, as well as keeping car vents closed when driving.

Researchers conducted a community dwelling cohort of more than 1,300 women ages 70 to 89 beginning in 2005, with a 5 year followup. They used MRI data to analyze high-dimensional gray matter atrophy in brain areas vulnerable to Alzheimer’s disease, including the amygdala, hippocampus, parahippocampal gyrus, thalamus, inferior temporal lobe areas and midbrain.

The participant’s home address was used to obtain air monitoring data to determine exposure to pollution and estimates for a three year average exposure to particulate matter 2.5 (PM 2.5) before the first MRI was conducted, then up to two brain MRI scans were conducted up to five years later.

PM 2.5 is air pollution particles the size of 2.5 micrometers or smaller, roughly 70 times smaller than the diameter of one human hair. PM 2.5 is a mixture of soot and dirt so small the particles are easily inhaled into the lungs and move to the blood stream leading to side effects, such as increased risk of early death, increased risk of stroke and cardiac arrest.

Prior to exposure to increased levels of PM 2.5, there was no association between exposure and Alzheimer’s disease. After exposure to increased levels, a link was found between Alzheimer’s disease and air pollution.

Each 3-μm increase of PM 2.5 was linked with an increase in brain shrinkage, the equivalent of 24% increased risk of developing Alzheimer’s disease.

“Late-life exposure to PM2.5 is associated with increased neuroanatomical risk of Alzheimer’s disease, which may not be explained by available indicators of cerebrovascular damage,” wrote study authors.

Furthermore, the link between air pollution was present even at levels below what U.S. regulatory standards deem as “safe.”

Other studies have shown that even short-term exposure to air pollution can lead to side effects. Research published earleir this year found that low levels of air pollution exposure can increase the risk of Dementia. Even at levels below international safety standards the health risks were still present.

The association was still relevant after adjusting for socio-demographics, intracranial volume, lifestyle, clinical characteristics, and white matter lesions.

Research conducted last year indicated PM 2.5 air pollution kills nearly 30,000 Americans every year. Particulate matter air pollution presents serious consequences to the global population and increases the risk of many health conditions.