Air pollution increases the risk of dementia

November 11, 2025:

For a long time, it is well documented that air pollution can cause a long series of health problems that entail health costs. A new study "Lewy body dementia promotion by air pollutants" provides further evidence that exposure to PM2.5 increases such risks and costs.
 

The study analyzed hospital records of the 56.5 million US Medicare patients. Knowing the patients’ zip codes, the study found that long-term exposure to PM2.5 raised the risk of Lewy body dementia. 

Lewy body dementia and particulate matter

Dementia with Lewy bodies is a type of dementia characterized by changes in sleep, behavior, cognition, movement, and regulation of automatic bodily functions. The disease worsens over time and is usually diagnosed when cognitive impairment interferes with normal daily functioning. Lewy body dementia is the third most common form of dementia after Alzheimer’s disease and vascular dementia. Lewy bodies in the brain are made from a protein called alpha-synuclein.

Particulate matter (PM) are microscopic particles of solid or liquid matter suspended in the air. PM2.5 are microscopic particles that are smaller than 2.5 thousandths of a millimeter.  

Test on mice

To see if air pollution could trigger Lewy bodies, the research team also exposed mice to PM2.5 pollution every other day for 10 months. Some were normal mice, but others were genetically modified to prevent them making alpha-synuclein. The results were convincing. In normal mice, nerve cells died off, leading to brain shrinkage and cognitive decline. The genetically modified mice were largely unaffected.

The MARCHES project

The study confirms that air pollution has serious impacts on human health by increasing the risk of Lewi body dementia and therefore also on general health costs. The MARCHES project is a 4-year EU-funded research project which aims to improve methodologies to assess the health costs of environmental stressors. Together with water contamination, air pollution is one of the focus areas of the MARCHES project. 

Strong association

“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,” said Ted Dawson, a senior author on the study and a professor in neurodegenerative diseases at Johns Hopkins University in the US to the Guardian.

“Unlike age or genetics, this is something we can change,” said Dr Xiaobo Mao, neurologist at Johns Hopkins and the study’s lead investigator, according to The Guardian. “The most direct implication is that clean air policies are brain health policies.”

The relation between air pollution and diseases such as asthma, lung cancer and chronic obstructive pulmonary disease (COPD) is well documented. This study confirms that Lewy body dementia can be added to the list.

"A major part of the MARCHES project is to improve the methodologies for inclusion of relevant diseases when estimating the health costs of air pollution. A review by a team of WHO appointed experts already added dementia to a list of diseases for which links to air pollution exposures are considered credible (Forastiere et al., 2024).  With the new study published in Science, more subtypes of dementia seem to be contributing to the health costs from air pollution," said MARCHES project coordinator, professor Mikael Skou Andersen, Department of Environmental Science , Aarhus University. 

The study "Lewy body dementia promotion by air pollutants" was published in Science in September 2025. www.science.org/doi/10.1126/science.adu4132