New research has found a significant link between neighborhood socioeconomic status and the cognitive abilities of older individuals, irrespective of underlying brain pathologies commonly associated with dementia. The findings, which have been published in in the journal Alzheimer’s & Dementia, suggest that one’s living conditions are closely related to their brain’s resilience to decline in later life.
The rationale for this investigation stems from the observation that, despite significant advances in understanding the neuropathological underpinnings of dementia, including Alzheimer’s disease and related conditions, there remains a notable discrepancy in how these biological markers correlate with cognitive decline across different individuals.
Interestingly, some people maintain robust cognitive functions even in the presence of substantial neuropathological changes. This phenomenon suggests the existence of a cognitive reserve—a concept proposing that certain life experiences and attributes can provide a protective buffer against cognitive deterioration.
Previous research has linked individual socioeconomic factors, such as income, education, and occupation, to cognitive outcomes. Additionally, emerging studies have begun to shed light on the role of neighborhood-level socioeconomic factors, showing that living in areas marked by higher levels of deprivation is associated with worse cognitive outcomes and an increased risk of dementia. These findings raise questions about the mechanisms through which neighborhood disadvantage may influence brain health.
The study utilized data from the Integrated Neurodegenerative Disease Database at the Center for Neurodegenerative Disease Research, focusing on 469 autopsy cases spanning from 2011 to 2023. All these cases had detailed post-mortem neuropathological data and demographic information, including the last known Mini-Mental State Examination (MMSE) scores — a screening tool used to assess cognitive function, including memory, orientation, attention, language, and visuospatial skills.
For the assessment of neighborhood socioeconomic status, the researchers utilized the Area Deprivation Index (ADI), a geographic-based metric that encapsulates various aspects of neighborhood deprivation, including poverty, unemployment, education, and housing quality.
“There is strong evidence that sociodemographic factors affect cognition in the elderly, but the mechanisms that underlie this effect were not clear,” explained study author Edward B. Lee, an associate professor at the University of Pennsylvania, co-director of the Institute on Aging, and principal investigator at the Translational Neuropathology Research Laboratory.
“We had an opportunity to look at (1) area deprivation index (as a measure of neighborhood-level social determinants of health), (2) cognition as measured by MMSE, and (3) neuropathologic change seen at autopsy. By looking at these three factors, we were able to surmise how neighborhood disadvantage might affect cognitive function.”
The researchers found that higher neighborhood disadvantage was associated with lower cognitive abilities. This relationship persisted even after adjusting for various confounding factors, such as age, sex, race, and education level.
However, higher neighborhood disadvantage was not associated with a higher burden of dementia-related neuropathologies. In fact, individuals from more disadvantaged neighborhoods tended to have a lower overall burden of neuropathological changes traditionally linked with dementia, including Alzheimer’s disease neuropathologic change, Lewy body dementia, and limbic-predominant age-related TDP-43 encephalopathy.
Importantly, the researchers found that the association between neighborhood disadvantage and reduced cognitive function remained significant even when controlling for neuropathological changes. This suggests that the impact of socioeconomic factors on cognition operates through mechanisms beyond the accumulation of pathological lesions associated with dementia.
“The neighborhood one lives in affects your health where more disadvantaged environments appears to negatively affect brain function,” Lee told PsyPost. “We wanted to know whether this effect was due to the accumulation of neurodegenerative disease pathologies such as Alzheimer’s disease neuropathologic change. We did not see this. Rather, the effect of neighborhood disadvantage on cognition was independent of these brain pathologies. This means that neighborhood disadvantage affects one’s ‘cognitive reserve.'”
The researchers also uncovered that higher educational attainment seemed to mitigate the adverse effects of neighborhood disadvantage on cognitive function.
“Educational attainment is another such ‘cognitive reserve’ factor where more education appears to make the brain resilient against neuropathologies such as Alzheimer’s disease,” Lee said. “Interestingly, we saw that the effect of neighborhood disadvantage was reversed by educational attainment. This suggests that policies that promote equitable resource allocation, such as enhanced educational opportunities for disadvantaged communities, may have an impact on dementia.”
However, the study is not without its limitations. Most notably, the cohort was predominantly White and non-Hispanic, limiting the generalizability of the findings across different racial and ethnic groups. Additionally, the cross-sectional nature of the study and the reliance on autopsy cases from individuals likely to have higher education and live in less disadvantaged neighborhoods may have influenced the results.
“This study was based on a research autopsy cohort where having good representation of diverse racial and ethnic groups has been difficult to achieve,” Lee explained. “Additional studies on minoritized populations would be informative. In addition, there were very few cases with severe cerebrovascular disease (as a reflection of how cases were recruited into our clinical studies) and so one should be cautious about drawing strong conclusions about the relationship between ADI and cerebrovascular disease from this study.”
Despite these limitations, the study offers important evidence that neighborhood socioeconomic status can impact cognitive health, independent of the direct effects of brain pathologies.
Regarding the long-term goals for the research, Lee said that “while my laboratory has long been interested in how certain genetic (DNA) variants affect downstream neurodegenerative disease pathologies, there has been a consistent downward trend in dementia incidence in several developed countries. Thus, we will continue to expand our studies to better understand how environmental factors affect the brain and cognition.”
The study, “Neighborhood disadvantage reduces cognitive reserve independent of neuropathologic change,” was authored by Boram Kim, Isabel Yannatos, Kaitlin Blam, Douglas Wiebe, Sharon X. Xie, Corey T. McMillan, Dawn Mechanic-Hamilton, David A. Wolk, and Edward B. Lee.