Researchers from the University of Florida have determined that even modest increases in the levels of particulate matter (PM) and nitrogen dioxide ($\text{NO}_2$) correlate with a heightened susceptibility to developing both dementia with Lewy bodies and Parkinson’s disease dementia. These findings were presented in the journal JAMA Network Open.
As part of a retrospective cohort investigation, the scientists reviewed the medical records of over 2.1 million individuals in Denmark, aged 65 to 95, covering the period from 2001 through 2021.
Throughout the follow-up duration, three thousand participants were diagnosed with dementia with Lewy bodies (DLB), and 3,800 developed dementia associated with Parkinson’s disease (PDD). By utilizing the participants’ residential addresses over a span exceeding a decade, researchers were able to reconstruct estimates of individual exposure to these air pollutants.
The analysis revealed that every incremental rise in airborne particulate concentration correlated with an almost fourfold increase in the risk of DLB onset, and more than a twofold increase for PDD. While the impact of nitrogen dioxide was less pronounced, it remained statistically significant: greater $\text{NO}_2$ exposure was linked to nearly doubling the likelihood of developing dementia with Lewy bodies.
The authors point to the underlying pathological mechanism for both DLB and Parkinson’s disease: abnormal clumps of the alpha-synuclein protein aggregating within neurons, known as Lewy bodies. These inclusions disrupt vital neurochemical processes, leading to progressive impairments in cognition, motor skills, and behavior.
It appears these pollutants act as triggers for neuroinflammation. As explained by the lead investigator, Professor Dmitry Davydov from the Norman Fexel Institute, particulate matter and nitrogen dioxide are commonly generated through vehicular traffic, maritime transport, and fuel combustion. Their microscopic dimensions enable them to enter the bloodstream upon inhalation and subsequently traverse the blood-brain barrier.
“We already understand that constituents of polluted air spark inflammation in the cardiac and pulmonary systems. It seems they exert a similar disruptive effect on the brain,” the researchers concluded.
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