A study drawing on health data from nearly 30 million people suggests long-term exposure to air pollution may contribute to memory loss, cognitive decline and a heightened risk of dementia.
To determine how air pollution impacts dementia risk, scientists from the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge conducted a large-scale review and meta-analysis of dozens of studies with health data on over 29 million people. The study was reported by SciTechDaily
Researchers were able to draw more reliable conclusions by including a wide range of studies, some with conflicting outcomes. The results implicate some of the most common forms of air pollution. With dementia risks increasing 3 to 17 percent for every 10 micrograms per cubic meter, depending on the pollutant, their findings underscore the need to confront this problem head on.
“Stricter limits for several pollutants are likely to be necessary,” joint first author Clare Rogowski from the MRC Epidemiology Unit told SciTechDaily, stressing the urgent need for policy inventions at every level of government.
Researchers found a positive and statistically significant association between dementia and three types of air pollution: nitrogen dioxide, soot and fine particles called PM 2.5.
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Measuring no more than 2.5 microns in diameter, PM 2.5 arises from a wide variety of sources, from vehicle exhaust to construction dust to complex chemical reactions involving other pollutants in the atmosphere. Vehicle exhaust, wood stoves and wildfires are among the sources of soot, a type of PM 2.5 generated by combustion.
Nitrogen dioxide, meanwhile, is a key pollutant created by the burning of fossil fuels, emitted by everything from vehicles to gas stoves to industrial processes.
These pollutants likely contribute to dementia risk by causing inflammation in the brain and oxidative stress, a chemical process that can lead to cell damage in the body. Both are known to play a role in the onset and progression of dementia.
With air pollution, the effect may result from direct entry to the brain or through the same mechanisms underlying lung and cardiovascular diseases. It can also penetrate deep into the lungs, triggering inflammation there and in other organs.
“Preventing dementia is not just the responsibility of healthcare,” joint first author Dr Christiaan Bredell from the University of Cambridge told SciTechDaily. “This study strengthens the case that urban planning, transport policy, and environmental regulation all have a significant role to play.”
