Air pollution exposure may increase risk of Alzheimer’s disease

By Imogen Howse via SWNS

People exposed to higher levels of air pollution are more likely to show signs of Alzheimer’s disease in their brain, according to a new study.

Scientists examined the brains of 224 people who agreed to donate their bodies to further dementia research after they died.

The team from Emory University in Atlanta studied measures of Alzheimer’s in the participants’ brains – namely, the number of amyloid plaques and tau tangles – and compared this to the traffic-related air pollution exposure found at their homes.

They discovered that those who had higher levels of air pollution exposure before death – which for this group, happened at an average age of 76 – had higher levels of amyloid plaques in their brains.

Results showed that people who had 1 µg/m3 higher PM2.5 exposure in the year before death were nearly twice as likely to have higher levels of plaques, while those with 1 µg/m3 higher PM2.5 exposure in the three years before death were nearly nine times (87 percent) more likely to have higher levels of plaques.

The average level of exposure was 1.32 micrograms per cubic meter (µg/m3) in the year before death and 1.35 µg/m3 in the three years before death.

This was measured via fine particulate matter (PM), which consists of pollutant particles of less than 2.5 microns in diameter (PM2.5).

Study author Dr. Anke Huels said: “These results add to the evidence that fine particulate matter from traffic-related air pollution affects the amount of amyloid plaque in the brain.”

She stressed however that this does not mean air pollution causes more amyloid plaques in the brain – and by extension Alzheimer’s. It only proves an association between the two.

“More research is needed to investigate the mechanisms behind this link,” she explained.

The study, published in the journal Neurology, also investigated whether having the main gene variant associated with Alzheimer’s disease, APOE e4, had any effect on the relationship between air pollution and signs of Alzheimer’s in the brain.

Researchers found that the strongest relationship between air pollution and signs of Alzheimer’s was among those without the gene variant.

Dr. Huels added: “This suggests that environmental factors such as air pollution could be a contributing factor to Alzheimer’s in patients in which the disease cannot be explained by genetics."

She says further research will be needed to confirm the findings.