Air pollution can drive devastating forms of dementia, study suggests

Fine-particle air pollution can trigger toxic brain protein clumps that drive Lewy body dementia, researchers say.

The particles, known as PM2.5, cause proteins in the brain to misfold into clumps that damage nerve cells.

These clumps are a hallmark of Lewy body dementia – the third most common type of dementia after Alzheimer’s and vascular dementia.

Dr Xiaobo Mao, a neurologist at Johns Hopkins and lead investigator., said: “Unlike age or genetics, this is something we can change.

“The most direct implication is that clean air policies are brain health policies.”

Researchers reviewed hospital records of 56.5m US Medicare patients.

They examined those admitted for the first time between 2000 and 2014 with the protein damage, and estimated long-term exposure to PM2.5 – airborne particles smaller than 2.5 thousandths of a millimetre that can lodge in the lungs, bloodstream and brain.

They found long-term exposure increased the risk of Lewy body dementia, but had less impact on another brain disease not driven by toxic proteins.

In lab experiments, mice exposed to PM2.5 every other day for 10 months showed nerve cell loss, brain shrinkage and memory problems.

But mice genetically altered to block alpha-synuclein – a protein crucial for normal brain function – were largely unaffected.

Alpha-synuclein can misfold in different ways to produce harmful Lewy bodies that spread through the brain, killing nerve cells and causing severe symptoms.

Further work in mice showed that PM2.5 pollution drove aggressive, resilient and toxic clumps of alpha-synuclein resembling human Lewy bodies. Although conducted in animals, the findings are seen as compelling evidence.

The results have prompted fresh calls for tougher air quality measures, including lower industrial emissions, improved wildfire controls and less domestic wood burning.

Ted Dawson is senior author of the study and professor of neurodegenerative diseases at Johns Hopkins.

He said: “Putting the two together, to me, indicates that there’s a pretty strong association with air pollution causing Lewy body dementia.

“We think it’s a very important driving factor for dementia.

“There needs to be a concerted effort to keep our air clean.”

The work builds on earlier research showing PM2.5 particles lodged in the brain have been linked to Alzheimer’s and to cognitive decline.