The elderly and those vulnerable to risks of Alzheimer's disease need to better protect themselves from air pollution, according to a recent study led by Fudan University that showed long-term exposure to PM2.5 increased the risk of cognitive impairment.

The study, titled "Association of Long-term Exposure to Ambient Air Pollution with Cognitive Decline and Alzheimer's Disease-related Amyloidosis", was published in the journal of Biological Psychiatry on May 18.

It concluded that individuals exposed to high levels of PM2.5－small airborne particles measuring 2.5 micrometers or less in diameter－are more vulnerable to the risk of getting Alzheimer's, an illness that causes a decline in cognitive thinking, and behavioral and social skills. An increase of 20 micrograms per cubic meter of PM2.5 exposure can increase the risk of cognitive decline by 10 percent.

"Air pollution induces neurotoxic reactions and may exert adverse effects on cognitive health," the study said.

The study provided key molecular epidemiological evidence that PM2.5 impairs cognitive function through amyloid, a protein in the brain, which proved air pollution-induced cognitive decline.

Teams from the School of Public Health at Fudan University in Shanghai and the university's affiliated Huashan Hospital led the study.

Chen Renjie, a professor of environmental health from the school and a team leader on the study, said the incidence of Alzheimer's continues to increase with the aging of China's population, and factors that affect the disease need deeper research.

Based on the research results, he suggested that nursing homes should be located away from air pollution sources.

"It is not a good thing that many nursing homes in China are now built in downtown areas, where air pollution is more severe due to heavier vehicle emissions. The elderly should be more informed about things such as placing an air purifier in their bedrooms to reduce exposure to air pollution," he said.

The study was conducted using a population-based survey involving 31,573 random participants from counties and cities in 22 provinces. They investigated cognition ability via questionnaire results matched against localized air quality data for each respondent from 2008 onward.

From 2017, about 1,100 cognitively unimpaired participants were selected in Qingdao, Shandong province, between the ages of 40 and 90, and tests were carried out on their cerebrospinal fluid, the key bio-sample for Alzheimer's, and determined whether their cognitive functions had been affected by the environment.