Breathing Danger: Study Links Air Pollution to Lewy Body Dementia Risk   

For years, researchers have suspected that the air we breathe might affect our brain health. Now, a study examining 56.5 million Americans reveals a troubling connection between living in a place with higher air pollution and Lewy body dementia (LBD) — a finding with significant implications for the Parkinson's disease (PD) community, as 75-80% of people with Parkinson's eventually develop LBD. 

Lewy body dementia is an umbrella term for two related conditions: dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). Both involve the accumulation of abnormal protein deposits called Lewy bodies — which contain clumps of alpha-synuclein protein — throughout the brain. While people with Parkinson's initially experience movement symptoms like tremor and rigidity due to Lewy bodies primarily in neurons within movement-control brain regions, most will eventually develop cognitive symptoms as these protein deposits spread to areas controlling memory and thinking. 

The study, which was supported by the Parkinson’s Foundation and led by 2019 Stanley Fahn Jr. Faculty Award recipient Xiaobo Mao, analyzed health records of 56.5 million Americans who used Medicare from 2000 to 2014, across 34,824 zip codes. Researchers matched the zip codes to exposure to PM2.5, tiny particles in the air that come from sources like vehicle exhaust, industrial emissions and wildfire smoke. These particles are so small they can penetrate deep into the lungs and the bloodstream. While PM2.5 is recognized as a health concern and risk factor for dementia, this is the first study to find a link between PM2.5 and Lewy body dementia.  

Study Results 

The analysis showed that there was a strong link between long-term PM2.5 exposure and higher risk for someone’s first hospital admission for LBD, indicating that living in a place with more air pollution is associated with a greater risk for LBD. 

To understand how air pollution could be connected to LBD, the researchers conducted experiments with mice. They found that long-term PM2.5 exposure caused brain shrinkage and cognitive deficits in normal mice, lending support to their initial findings. Interestingly, this effect disappeared in genetically engineered mice lacking alpha-synuclein—the protein that forms the characteristic Lewy bodies. This suggests that alpha-synuclein plays a crucial role in how air pollution damages our brains. 

Perhaps most striking, the research team discovered that PM2.5 exposure in mice engineered to display Parkinson's-like symptoms led to the development of what they call “PM-PFF”—a particularly harmful version of alpha-synuclein that is highly resistant to breakdown and especially toxic to brain cells. The team showed that this corrupted protein closely resembles the abnormal alpha-synuclein found in actual LBD patients.  

When the researchers exposed mice engineered to develop Parkinson's-like symptoms to air pollution samples from China, the U.S. and Europe for two months, they all consistently produced dangerous “PM-PFF” protein formations, suggesting air pollution is a global concern to brain health. 

The team also compared gene expression activity patterns between PM2.5-exposed normal mice and human LBD patients, finding prominent similarities. This pattern match strengthens the evidence that air pollution isn't just correlated with dementia—it may actually cause the biological changes seen in the disease. 

Highlights 

• The study analyzed health records of 56.5 million Americans who used Medicare in a 14-year period, residing in 34,824 zip codes. 

• Living in an area with higher air pollution (higher long-term levels of PM2.5 particles) was linked to hospitalization for Lewy body dementia (LBD). 

• In normal mice, long-term PM2.5 exposure caused brain shrinkage and cognitive deficits. These issues depended on the presence of alpha-synuclein, a protein associated with PD and LBD.  

• In mice engineered to develop Parkinson's-like symptoms, PM2.5 exposure created what they call “PM-PFF”—a particularly harmful version of alpha-synuclein that's highly resistant to breakdown and especially toxic to brain cells. 

• Gene activity patterns in PM2.5-exposed normal mice were similar to those in human LBD patients. 

What Does This Mean? 

This research provides the first clear biological explanation for how air pollution might trigger or accelerate the development of Lewy body dementia. The identification of PM2.5 as a specific risk factor means we now have a measurable, modifiable environmental target for disease prevention. 

This study, and others like it, have found a clear association between environmental toxicants and neurodegenerative diseases – which is important as this knowledge could inform and impact environmental policies.  

This study highlights the importance of reducing exposure to air pollution when possible and continuing proactive steps that support brain health, like regular exercise, quality sleep and staying proactive with medical care. 

What do these findings mean to the people with PD right now? 

While this research doesn’t change day-to-day treatment for people with PD right now, it strengthens what many in the Parkinson’s community have long suspected — that environmental factors play a real role in disease development and progression. Knowing that air pollution may contribute to Lewy body disease gives us a new area to monitor and advocates another reason to push for cleaner air and stronger environmental standards. 

If you are concerned about exposure to air pollution, or PM2.5 particles, talk to your doctor.  

Learn More 

The Parkinson’s Foundation believes in empowering the Parkinson’s community through education. Learn more about PD and the topics in this article through our below resources, or by calling our free Helpline at 1-800-4PD-INFO (1-800-473-4636) for answers to your Parkinson’s questions. 

• Golf Course Pesticides, Drinking Water & Parkinson’s Risk 

• Environmental Factors 

• Episode 122: Environmental Factors and Parkinson’s