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Does Air Pollution Damage our Brains? #AustraliaBurns

Thursday, December 19th, 2019

Air quality readings across Australia are at concerning levels right now in the wake of the bushfires. Known as PM2.5, rates of particle matter smaller than 2.5 micrometres are easy to inhale and can cause health problems. A new study suggests that these tiny pollutants particles might even change the structure of our brain.

Measuring the link between pollution and brain function

The US study analysed the data of 998 females aged 73–87 years without dementia, all of whom were enrolled in a large-scale study of women’s health[1].  The women were followed for roughly 11 years. Each year, the women completed tests of learning and memory; and their brains scanned twice, five years apart. Magnetic resonance imaging (or MRI) was used to detect brain atrophy, or wasting, with this deterioration scored on its degree of similarity to the brain atrophy characteristic of Alzheimer’s disease. Environmental Protection Agency data was then matched to the women’s residential addresses to estimate their degree of exposure to PM2.5 pollution.[2]

Shrinking brains due to pollution may contribute to memory decline

The researchers found that the greater the women’s exposure to PM2.5, the greater their decline in learning new information and recalling that information later. This association remained even after the team adjusted the results to account for lifestyle factors such as income, smoking status and level of education. The brain scan results suggested that this was due to increased PM2.5 exposure being linked to increased brain atrophy – even before cognitive signs of dementia appeared. Interestingly, a recent systematic review has concluded that greater exposure to airborne pollutants such as PN2.5 does not influence cognition alone.[3]

The US study did not investigate or rule out other types of pollutants or environmental factors that might have been responsible for the findings. Nor did it estimate the women’s exposure to PM2.5 in their earlier years of life. We also cannot know if these findings would generalise to men. This study was a high-quality study, adding further evidence to the earlier systematic review. The combination of MRI and cognitive function data together, and over a long period of time, helps us to more confidently understand how structural changes in the brain determine the cognitive changes seen in dementia.