Living in socioeconomically disadvantaged neighborhood has been linked to a number of negative health outcomes, such as higher rates of cardiovascular diseases, diabetes, and premature mortality. A new study led by UC San Francisco researchers suggests that a similar relationship exists between neighborhood disadvantage and late-life cognitive impairment, resulting in increased risk for Alzheimer disease and related dementias (ADRD).
The study, published online in JAMA Neurology on July 19, is believed to be the first to investigate the connection between neighborhood socioeconomic deprivation and late-life cognitive impairment using a diverse, nationally representative sample.
“One of the things that we’ve become very interested in is how somebody’s background, their social exposome, if you will—factors like income, socioeconomic status, quality of education, even discrimination, stress, et cetera—all of these factors somehow might make the brain more vulnerable to getting dementia,” explained senior author Kristine Yaffe, MD, during a recent episode of the JAMA Neurology Author Interviews podcast. Yaffe is the Scola Endowed Chair, Epstein Endowed Chair, and a professor of psychiatry, neurology, and epidemiology at UCSF, as well the Department of Psychiatry and Behavioral Sciences' vice chair for the Weill Institute for Neurosciences. She is also the director of neuropsychiatry and director of the Memory Evaluation Clinic at the San Francisco VA Medical Center and director of the UCSF Center for Population Brain Health.
Largest study of its kind combined health, demographic, and geographic data to paint a more complete picture of dementia risk factors
To explore the issue, researchers assembled a cohort of more than 1.6 million participants by using a random sample of Veterans Health Administration (VHA) patients aged 55 or older who received VHA care between October 1999 and September 2021. Eligible participants also had to have had at least one visit and no diagnosis of prevalent ADRD in the two years prior to their inclusion in the study and at least one follow-up visit.
Utilizing VHA patient data allowed the study group to put together a sample population that more accurately reflected the diversity of the general U.S. population and a wider range of socioeconomic conditions than previous studies. It also allowed researchers to ensure that participants had relatively equal access to health care services.
“One of the challenges when we’re looking at some of these social determinants of health factors and trying to look at outcomes—regardless of what the outcome is—you don’t know how much could be related to access to care,” explained Yaffe. “…The nice thing about the VA is that everyone has access to care.”
Health and demographic data were paired with 9-digit address ZIP code information, allowing researchers to determine each participant’s Area Deprivation Index (ADI) value based on their specific location. ADI is a measure that combines 17 indicators (including income, education, employment, and housing) to determine severity of socioeconomic disadvantage at the neighborhood level. Participants were then grouped into quintiles based on their ADI rank for comparison and analysis.
Significant differences found in dementia incidence across ADI groups
Participants were followed for an average of 11 years until they developed dementia, died, or had their last medical encounter. 12.8% of the study population developed dementia during their follow-up period.
After adjusting for demographic characteristics and comorbid conditions associated with higher dementia risk in veterans, researchers discovered that participants living in the most disadvantaged neighborhoods had the highest risk for developing dementia. Overall, the data revealed a strong, linear association between levels of neighborhood disadvantage and an increased risk of dementia, showing that neighborhood socioeconomic factors play a definite and profound role in brain health outcomes independent of individual and health care system-related factors.
The finding, according to the study authors, “underscores the importance of the social exposome and social vulnerability of dementia risk, even in a population enrolled in the largest national, integrated health care system in the United States.”
They agree that continued research is needed on the association of ADRD and neighborhood socioeconomic disadvantage to understand the potential pathways involved and provide further valuable insight to guide future research, public policies, community interventions, and social and health care efforts to prevent and treat ADRD.
Co-authors: In addition to Yaffe, authors included Christina S. Dintica, PhD (first author), and Amber Bahorik, PhD, of the UCSF Department of Psychiatry and Behavioral Sciences; Feng Xia, MPH, of the Northern California Institute for Research and Education; and Amy Kind, MD, PhD, of the University of Wisconsin School of Medicine and Public Health.
Funding: This study was supported by an Alzheimer’s Association grant AARF-21-851960 (Dintica), National Institute on Aging grant R35 AG071916 (Yaffe), and Department of Defense grant W81XWH-22-1-0961 (Yaffe).
Conflicts of interest: Dintica reported receiving grants from the Alzheimer’s Association during the conduct of the study. Kind reported receiving grants from the National Institutes of Health (NIH) during the conduct of the study, as well as outside the submitted work. Yaffe reported receiving grants from NIH, serving on the data and safety monitoring boards for several NIH-sponsored studies, serving as a board member of Alector, being a consultant for Alpha Cognition, being a member of the Beeson scientific advisory board, receiving personal fees from Eli Lilly, and serving on the data and safety monitoring board for Eli Lilly outside the submitted work.
Learn more: Yaffe was interviewed on the JAMA podcast about this research. You can find the interview here.