A new study from the University of Georgia College of Public Health focuses on the powerful role our surroundings play in shaping dementia risk. Led by Assistant Professor of Health Policy and Management Suhang Song, this meta-analysis demonstrates that factors including air pollution and access to green or blue spaces can significantly raise or lower the odds of cognitive decline and developing dementia.

“These numbers show that living in a dementia-friendly environment is important to delay or prevent cognitive decline and the onset of dementia,” Song said.

Conducting the meta-analysis was important, as was taking several empirical studies to create a clearer picture about environmental risk, Song said. The research combined 54 studies in a systematic review and 21 in the meta-analysis, enabling researchers to quantify the impact of several factors.

While past research has shown the association between environmental factors and dementia risk, Song said the contributions of some factors were worth noting.

Environmental factors could increase dementia risk by 10%

Living near major roadways was associated with a roughly 10% higher risk of dementia, and exposure to fine particulate matter in the air — something that is generated by vehicles and industrial emissions — was associated with a 9% increase in risk. Nitrous Oxide increased risk by 10%, and noise pollution was shown to increase risk by about 9%.

Alternatively, some built environments help reduce the risk of cognitive decline. Green and blue spaces, which include built and natural parks as well as bodies of water, reduced risk by about 6%. Walkability in a community, as well as access to local amenities including food stores, community centers and health care, also reduced risk.

“Based on these findings, we can suggest that people visit parks or forests more often and also live further from the major roads,” Song said. “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.”

Improving urban planning

This data can help inform urban planning efforts moving forward to create more communities that foster cognitive health, Song said.

“The biggest advantage of this paper is to quantify the association between certain factors and cognitive health,” Song said. “This analysis can provide evidence for data-driven urban planning and support decision makers.”

Summarizing objective measurements of environmental factors for future research

This systematic review and meta-analysis focused on studies using objectively measured environmental factors, which may reduce the bias associated with subjective measures such as perceptions of air quality or individual reports of greenspace and an area’s beauty. These instances of self-reported data can sometimes limit the reliability of a study’s conclusions.

Song hopes this study will serve as a foundation for future research, encouraging researchers to prioritize objective measurements in investigating environmental influences on cognition and dementia risk.