Exposure to higher levels of fine air pollutants may cause decline in memory, and lead to Alzheimer's-like brain damage, according to a study carried out in elderly women. Researchers from the University of Southern California (USC) in the US noted that fine particles, also called PM2.5 particles, are about 1/30th the width of a human hair.
These particles come from traffic exhaust, smoke and dust and their tiny size allows them to remain airborne for long periods, get inside buildings, be inhaled easily, and reach and accumulate in the brain. For an increase of 2.81 microgrammes per cubic metre of PM2.5, the annual memory decline rate was accelerated by 19.3 per cent, the researchers found. Fine particle pollution is associated with asthma, cardiovascular disease, lung disease and premature death, they said.
The study, published in the journal Brain, touches on the renewed interest in preventing Alzheimer's disease by reducing risk, and also hints at a potential disease mechanism. "This is the first study to really show, in a statistical model, that air pollution was associated with changes in people's brains and that those changes were then connected with declines in memory performance," said Andrew Petkus, assistant professor at USC.
"Our hope is that by better understanding the underlying brain changes caused by air pollution, researchers will be able to develop interventions to help people with -- or at risk -- for cognitive decline," Petkus said in a statement. Previous research has suggested that fine particle pollution exposure increases the risk for Alzheimer's disease and related dementias.
What scientists haven't known is whether PM2.5 alters brain structure and accelerates memory decline. They used data from 998 women, aged 73 to 87, who had up to two brain scans five years apart. Those brain scans were scored on the basis of their similarity to Alzheimer's disease patterns by a machine learning tool that had been "trained" via brain scans of people with Alzheimer's disease.
The researchers also gathered information about where the 998 women lived, as well as environmental data from those locations to estimate their exposure to fine particle pollution. When all that information was combined, researchers could see the association between higher pollution exposure, brain changes and memory problems -- even after adjusting to take into account differences in income, education, race, geographic region, cigarette smoking and other factors.
"This study provides another piece of the Alzheimer's disease puzzle by identifying some of the brain changes linking air pollution and memory decline. Each research study gets us one step closer to solving the Alzheimer's disease epidemic," Petkus said.