Genetics, Social Determinants Have Joint Impact on Cognitive Health

Genetics and community-level social determinants may interact to have a positive or negative impact on individuals’ cognitive health, a team from Florida Atlantic University (FAU) recently found.

The study, published in the journal Health & Place, indicated that the cognitive benefits of living in neighborhoods with greater access to social, walking, and retail destinations may be limited to people with a reduced genetic risk for cognitive decline.

Cognitive conditions like Alzheimer’s disease and dementia impact millions of Americans and result in soaring healthcare costs. The researchers stated that Alzheimer’s is the sixth leading cause of death in US, and more than 5.8 million people are living with the disease. By 2050, this number is expected to rise to nearly 14 million.

Additionally, the Alzheimer’s Association reports that in 2019, cognitive disorders cost the US $290 billion – an amount that could rise to $1.1 trillion by 2050.

Neighborhood environment may have a significant impact on an individual’s ability to maintain cognitive function with age, researchers noted. Because older adults spend less time outdoors, neighborhood environments increase in importance with age.

Physical aspects of a neighborhood, including the availability of sidewalks, parks, social, and walking destinations, may be associated with better cognitive function. However, few studies have evaluated how a neighborhood’s physical environment relates to cognition in older adults.

The FAU team conducted one of the first known studies to examine how cognitive functioning is affected by neighborhood environments depending on one’s apolipoprotein E (APOE) genotype, a genetic risk for Alzheimer’s.

Researchers categorized 4,716 participants from the Multi-Ethnic Study of Atherosclerosis as carriers of APOEε2 (lower Alzheimer’s risk), APOEε4 (higher Alzheimer’s risk), and APOEε3, the most common variant which is considered to have neutral risk for developing Alzheimer’s.

The results showed that individuals with a reduced genetic risk for cognitive decline, specifically APOE ε2 carriers, benefit most from living in neighborhoods with access to social, walking, and retail destinations.

"The positive influence of neighborhood environments on cognition may be strongest among individuals who are at the lowest risk for Alzheimer's disease," said Lilah M. Besser, PhD, MSPH, senior author who led the study, an assistant professor in FAU's School of Urban and Regional Planning within the College for Social Design and Inquiry, and a member of the FAU Brain Institute (I-BRAIN).

"The risk of cognitive decline among APOE ε4 carriers may be difficult to overcome even when living in beneficial neighborhood environments."

With age-related cognitive disorders on the rise in the US, researchers across the healthcare system are seeking out innovative ways to help prevent and treat these conditions. Many have discussed the important role genetics and precision medicine will play in understanding cognitive decline.

In a study recently published in Frontiers in Aging Neuroscience, a research team highlighted the potential for precision medicine and genetic testing to improve Alzheimer’s and dementia treatment.

“Taking a precision medicine approach, the question is no longer ‘Does treatment × work?’ but ‘Who does treatment × work for?’ Identifying the characteristics of ‘non-responders’ becomes as important as ‘responders’ in understanding the impact of a particular intervention,” the team on the said.  

“Such an approach may result in considerable health benefits by allowing more effective selection of individuals for treatments based on a priori known profiles of disease risk and their potential response to treatment.”

With their new study, FAU researchers have demonstrated the integral role social determinants of health also play in maintaining cognitive health, suggesting that treating these disorders will require stakeholders to consider genetics and neighborhood factors.

"Research on the potential influences of the neighborhood environment on cognition and brain aging can help inform recommendations for neighborhood improvements to simultaneously address population growth and healthy brain aging," said Besser. "Knowledge of how the neighborhood environment may affect cognition differentially depending on one's genetic makeup will be important to inform such recommendations."