Breathing in common air pollutants over many years may substantially raise a person’s risk of developing certain neurodegenerative diseases, pointing to an environmental driver for cognitive decline. A new study published in JAMA Network Open found that prolonged exposure to fine particulate matter and nitrogen dioxide is linked to higher rates of Lewy body dementia and Parkinson’s disease dementia. These results suggest that improving air quality could serve as a preventative measure to protect brain health in aging populations. Lewy body dementia and Parkinson’s disease dementia are related neurological conditions that severely impact memory, thinking, and behavior. Both disorders involve the abnormal buildup of a specific protein called alpha-synuclein in the brain. Proteins are the microscopic structures that carry out essential functions inside our cells. When these proteins misfold and clump together, they disrupt normal cellular activity and eventually cause brain cells to die. In Lewy body dementia, these protein clumps typically cause early cognitive problems, visual hallucinations, and unpredictable shifts in alertness. In Parkinson’s disease, the damage initially affects movement, causing tremors and stiffness, …