April 2, 2025
Where you live and spend time may play a powerful role in cognitive health, according to a new report. The findings add to growing evidence that environmental factors like exposure to air pollution or access to parks can affect the risk of developing Alzheimer’s disease or other forms of dementia.
For the analysis, researchers reviewed dozens of studies that looked at the effects of our environment on cognitive health and the risk of dementia. By pooling data from multiple studies, they quantified how much various environmental factors could increase or decrease the risk of cognitive decline and dementia.
Various forms of pollution increased dementia risk by up to 10 percent. Exposure to high levels of fine particulate matter in the air, a form of air pollution that is generated by vehicle exhaust, industrial emissions or wildfire smoke, was associated with a 9 percent increase in the risk of dementia. Exposure to high levels of nitrous oxide, another common air pollutant generated by agriculture, fossil fuel combustion, wastewater management or industrial processes, increased risk by 10 percent. Living in areas with high noise levels—so-called noise pollution—increased risk by about 9 percent, while living near major roadways, a source of both air and noise pollution, was associated with a roughly 10 percent higher risk of dementia.
Alternatively, some built environments helped reduce the risk of cognitive decline. Exposure to green areas like parks, or blue spaces like bodies of water, reduced dementia risk by about 6 percent. Living in communities that were easily walkable, providing access to food markets, community centers, or doctors’ offices, also reduced risk by several percent.
“These numbers show that living in a dementia-friendly environment is important to delay or prevent cognitive decline and the onset of dementia,” said study leader Suhang Song, an assistant professor of health policy and management at the University of Georgia College of Public Health.
“Based on these findings, we can suggest that people visit parks or forests more often and also live further from the major roads,” Dr. Song added. “Also, living in a community where there is more walkability, or being close to local amenities like bookstores, health care centers and more is helpful.” The findings were published in the journal Ageing Research Reviews.
It is difficult to establish a direct link between our environment and a disease like Alzheimer’s. Many factors are involved in who ultimately develops Alzheimer’s disease, and it is hard to pinpoint how environmental conditions may interact with these factors and impact the brain over many years.
But evidence continues to mount that our environment may be one important factor in long-term brain health. Exposure to pollutants may accelerate the buildup of toxic amyloid plaques in the brain, a hallmark of Alzheimer’s, and accelerate the onset of the disease in those who may already be vulnerable to developing it.
Spending time outdoors in parks and gardens or near lakes or the ocean, on the other hand, could help to lower levels of stress and promote increased physical activity and social interaction, which may reduce the risk of developing Alzheimer’s disease. Studies have also linked exposure to green spaces to a lower risk of depression, which has likewise been identified as a risk factor for Alzheimer’s disease.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D. Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Linlin Da, Xia Song, Zimu Jia, et al: “Objectively measured environmental features and their association with cognition and dementia: A systematic review and meta-analysis.” Ageing Research Reviews, February 2025
