A study has found that prolonged exposure to ultrafine dust can cause dementia. Dust particles that enter the body travel to the brain through the bloodstream, causing inflammation and leading to the abnormal aggregation of certain proteins in the brain.
A joint research team from Johns Hopkins University School of Medicine in the United States and the University of Cambridge in the United Kingdom noted, "Long-term exposure to ultrafine dust (PM2.5) with a diameter of 2.5 micrometers or less increases the risk of developing dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD)," and published their findings on 4th in the journal Science.
Dementia with Lewy bodies is the second most common type of dementia after Alzheimer's disease. It is a representative degenerative brain disease that shows motor impairments and dementia symptoms similar to Parkinson's disease. The protein alpha-synuclein (αSyn) aggregates inside brain cells to form Lewy bodies, and these protein clumps halt cellular functions. Parkinson's disease dementia occurs when dementia accompanies the loss of dopamine-producing nerve cells in Parkinson's disease.
The research team analyzed hospitalization records of 56.5 million patients with Lewy body and Parkinson's disease dementia in the U.S. from 2000 to 2014. As a result, those living in areas with high concentrations of ultrafine dust were at increased risk of hospitalization. The risk was 17% higher for patients with Parkinson's disease dementia and 12% higher for those with Lewy body dementia.
Similar results were confirmed in animal experiments. The research team exposed mice to ultrafine dust every other day for 10 months. Some were normal mice, while others were genetically modified mice that could not produce alpha-synuclein protein.
In normal mice, nerve cells died, causing the brain to shrink and impairing memory and learning abilities, while the genetically modified mice were hardly affected. Additionally, excessive alpha-synuclein accumulated in the brains of normal mice, and clumps of this protein were also found in the intestines and lungs.
Xiaobo Mao, a professor at Johns Hopkins University School of Medicine who led the study, explained, "Alpha-synuclein can spread from the intestines to the brain like a seed and may lead to dementia with Lewy bodies or Alzheimer's disease through the gut-brain axis." Ultrafine dust appears to accumulate in the lungs, causing inflammation before penetrating the blood-brain barrier (BBB) to reach the brain.
This study showed that ultrafine dust is not only a risk factor for dementia but can also directly affect the development of Lewy body and Parkinson's disease dementia by causing protein abnormalities in the brain. Ted Dawson, a professor at Johns Hopkins University School of Medicine, commented, "When combining both results, it shows a very strong correlation that air pollution causes dementia with Lewy bodies," emphasizing the need for efforts to keep the air clean.
Research on the impact of air pollution on our health is actively ongoing. The joint project 'Air Pollution and Dementia (RAPID)' by University College London (UCL) and the Francis Crick Institute, which started last year, is tracking the same issue. In 2023, this research team published findings in the journal Nature that ultrafine dust acts on cancerous mutations in lung tissue cells to cause lung cancer.
Charles Swanton, a professor and co-leader of the RAPID project, noted, "This study led by Johns Hopkins University is an important achievement that clarifies the process by which air pollution causes neurodegenerative diseases," adding that it has demonstrated the connection of ultrafine dust to the mechanisms of Lewy body dementia.
References
Science (2025), DOI: www.doi.org/10.1126/science.adu4132
Nature (2023), DOI: www.doi.org/10.1038/s41586-023-05874-3