Living near highways may raise the risk of dementia, mainly because of air pollution from traffic. Studies show people close to major roads face about a 10 percent higher chance of dementia compared to those farther away.
Air pollution from cars and trucks releases tiny particles and gases that can harm the brain over time. One large review of research found that living near big roads links to a risk ratio of 1.10 for dementia. This means a small but steady increase in odds for those nearby.
Traffic-related air pollution gets even worse when combined with other factors like past infections. For example, people with a history of infections who live very close to highways, within 50 meters of a major road, have up to 164 percent higher risk of Alzheimer’s disease and other dementias. This jumps to 349 percent in people without a certain gene called APOE4 that raises dementia odds on its own. High traffic pollution alone does not boost risk much, but it makes infections far more dangerous for the brain.
Better air quality helps lower this danger. In one study of older women, cleaner air over 10 years, with drops in particles like PM2.5 and nitrogen dioxide from traffic, cut dementia risk. Even after accounting for recent pollution levels, the improvement showed a clear benefit. This held true across ages, education levels, regions, and gene types.
Green spaces and roadside plants offer some protection. Trees and bushes near roads trap pollution particles on their leaves, pulling them out of the air we breathe. More neighborhood greenery also ties to lower dementia risk by fighting pollution effects.
Not everyone faces the same level of risk. Things like where you live in a city, smoking, or exercise can change how pollution hits. Urban dwellers and smokers seem more vulnerable, while staying active might shield the brain a bit.
Sources
https://cottonwoodpsychology.com/news/study-links-neighborhood-green-space-and-air-pollution-to-dementia-risk/
https://www.frontiersin.org/journals/dementia/articles/10.3389/frdem.2025.1668381/full
https://www.pnas.org/doi/10.1073/pnas.2107833119
https://pmc.ncbi.nlm.nih.gov/articles/PMC12754886/
https://www.crossroadspsychiatric.com/PatientPortal/MyPractice.aspx?UAID=%7BCA2E7E29-3E7F-46E6-9ECE-F2A9BC035B4B%7D&TabID=%7BX%7D&ArticleID=1710853597283
