Is there an association between dementia risk and neighborhood disadvantage?

By Pooja Toshniwal PahariaReviewed by Lily Ramsey, LLMJul 24 2023

In a recent study published in the JAMA Neurology Journal, researchers determined the association between the Area Deprivation Index (ADI) quintile and Alzheimer's disease and related dementias (ADRD) incidence among veterans registered in the United States (US) Veterans Health Administration (VHA) system.

Study: Dementia Risk and Disadvantaged Neighborhoods. Image Credit: LightFieldStudios/Shutterstock.com

Background

ADRD affects historically underrepresented and socially disadvantaged people disproportionately. Living in a low-income neighborhood may raise your risk of diabetes, cardiovascular disease, and early mortality.

This "social exposome" of social vulnerability, caused by social inequalities such as differences in the availability of nourishment, schooling, security, and recreational, cognitively, and physically beneficial activities, is linked to negative health outcomes in addition to individual-level factors such as social determinants of health.

The conditions may impact brain health and are linked to mild cognitive decline and ADRD risk, implying that an underprivileged social environment may be linked to late-life cognitive impairments. There has been limited research on the relationship between socioeconomic disadvantage in one's neighborhood and cognition.

About the study

In the present study, researchers investigated whether there was a difference in dementia incidence among VHA members by neighborhood disadvantage as assessed using the ADI.

Data from 2,398,659 VHA members aged ≥55.0 years were analyzed between October 1, 1999, and September 30, 2021. For every financial year, the team selected a 5.0% random sample. They excluded 492,721 individuals with inadequate ADI data, six with missing gender data, and 25,379 with dementia cases.

All the initially included 1,662,863 individuals were followed up at least once. The study's exposure was neighborhoods characterized by ADI values, which combined various sociodemographic variables (such as education, employment, housing, and income) into a disadvantage index based on census block groups. The individuals were ranked into different ADI quintiles based on the census block residential group.

For all individuals, demographic information (gender, age, ethnicity, and race) and Alzheimer's disease and related dementia diagnoses were obtained from the inpatient and outpatient records of the National Patient Care Databases and death data from the Vital Status File database. Dementia was diagnosed using the International Classification of Diseases, ninth and tenth revisions (ICD-9 and 10).

The outcome measures were time to dementia diagnosis, estimated by Cox proportional hazards modeling, used to calculate the hazard ratios (HRs), considering age groups as time scales.

The associations between educational attainment, household income, and ADI were determined. The team also evaluated the study findings' sensitivity using Fine-Gray-type proportional hazards modeling, adjusting for the competing death risk, and including income and education in the model.

The models were adjusted for post-traumatic stress disorder (PTSD), traumatic brain injury (TBI), current tobacco usage, depression, hypertension, dyslipidemia, and diabetes.

Results

The final study population comprised 1,637,484 individuals, among whom the mean age was 69 years; 98% were male; 0.4% were Asians; 9.30% were Blacks; 0.6% were Hispanics; 87% were Whites; and 3.0% were of unknown ethnicity or race. During 11 years of follow-up, 13% (208,909 individuals) of participants were diagnosed with dementia.

In comparison to individuals belonging to the least underprivileged neighborhood quintile, individuals in higher disadvantage block groups had increased dementia risk after adjusting for gender, ethnicity, race, and medical and psychiatric comorbidities (the first quintile was used as a reference, and the adjusted HR values for the second, third, fourth, and fifth quintiles were 1.1, 1.1, 1.2, and 1.2, respectively).

Repeating the primary study using competing risks for mortality and including educational attainment and household income in the models yielded similar findings. Blacks and Hispanics were more likely to live in the most disadvantaged neighborhoods.

All ADI groups had a high prevalence of cardiovascular risk factors, with those living in the most underprivileged neighborhood having higher risks of most medical conditions (except for dyslipidemia) than those in other quintiles.

Depression was similar across all groups, with a slightly higher prevalence among the most disadvantaged quintile. The prevalence rates of PTSD and traumatic brain injuries ranged between 0.2% and 6.7%, with a lower prevalence among the most underprivileged quintile group for PTSD. Collinearity was not demonstrated between education and the ADI quintile or household income and the ADI quintile.

Conclusions

The study findings showed that residing in disadvantaged neighborhoods increased dementia risks among US VHA veterans. The result highlights the importance of social exposure and vulnerability to dementia risk, even in the US's largest national, integrated healthcare system.

Addressing the social exposome in research, outreach, community-based care management, and policy is crucial, as it is an essential factor associated with health disparities.

Social exposure measures like ADI can help identify individuals at a higher risk of developing ADRD and inform clinical practices.

Future research should focus on understanding the lifespan repercussions of the social exposome and implementing a life course approach to understand how early-, mid-, and late-life social and environmental vulnerability affects brain health and the eventual risk of ADRD.