Is there a link between dementia risk and neighbor detriment?

In a recent study published in JAMA Neurology In the journal, researchers uncovered associations between regional deprivation index (ADI) quintiles and Alzheimer’s disease and related dementia (ADRD) incidence among veterans enrolled in the United States (US) Veterans Health Administration (VHA) system.

study: Dementia risk and disadvantaged areas. Image credit: LightFieldStudios/Shutterstock.com

Background

ADRD has been historically underrepresented and disproportionately impacts socially disadvantaged populations. Living in low-income areas can increase your risk of diabetes, cardiovascular disease, and early death.

This ‘social exposome’ of social vulnerability is driven by social inequalities such as differences in nutrition, schooling, security, and availability of recreational, cognitive and physically beneficial activities, and is associated with individual-level factors such as social determinants of health, as well as negative health outcomes.

This condition can affect brain health and is associated with mild cognitive decline and ADRD risk, suggesting that a disadvantaged social environment may be associated with late-life cognitive impairment. Studies on the relationship between socioeconomic disadvantage and cognition in neighborhoods are limited.

About research

In this study, researchers investigated whether there were differences in dementia incidence among VHA members by neighborhood detriment, as assessed using the ADI.

Data from 2,398,659 VHA members aged 55.0 and over were analyzed from 1 October 1999 to 30 September 2021. The team selected a 5.0% random sample for each fiscal year. They excluded 492,721 with insufficient ADI data, 6 with missing gender data, and 25,379 with dementia.

All 1,662,863 originally included had at least one follow-up. The study’s exposure was neighborhoods characterized by ADI values ​​that combined a variety of sociodemographic variables (education, employment, housing, income, etc.) to an unfavorable index based on census block groups. The individual was ranked in different her ADI quintiles based on census block residency group.

For all individuals, demographic information (sex, age, ethnicity, race), diagnosis of Alzheimer’s disease and related dementia were obtained from inpatient and outpatient records in the National Patient Care Databases and from mortality data from the Vital Status File database. Dementia was diagnosed using the International Classification of Diseases, 9th and 10th editions (ICD-9 and 10).

The outcome measure was time to dementia diagnosis, estimated by Cox proportional hazards modeling and used to calculate the hazard ratio (HR) considering age groups as the time scale.

Associations between educational attainment, household income, and ADI were determined. The research team also used Fine Gray-type proportional hazards modeling, adjusted for competing mortality risks, and included income and education in the model to assess the sensitivity of the findings.

Models were adjusted for post-traumatic stress disorder (PTSD), traumatic brain injury (TBI), current smoking status, depression, hypertension, dyslipidemia, and diabetes.

result

The final study population consisted of 1,637,484 individuals with a mean age of 69 years. 98% were male. 0.4% were Asian. 9.30% were black. 0.6% were Hispanic. 87% were white. 3.0% were of unknown ethnicity or race. During 11 years of follow-up, 13% of participants (208,909) were diagnosed with dementia.

After adjusting for sex, ethnicity, race, medical and psychiatric comorbidities, individuals in the more disadvantaged block group had increased dementia risk compared with individuals belonging to the most disadvantaged neighboring quintile (the first quintile was used as a reference, the adjusted HR values ​​for the second, third, fourth and fifth quintile were 1.1, 1.1, 1.2 and 1.2, respectively).

Repeating the first study using competing risks of mortality and including educational attainment and household income in the model yielded similar results. Blacks and Hispanics were more likely to live in the least advantaged areas.

All ADI groups had high prevalence of cardiovascular risk factors, and people living in the most disadvantaged areas had a higher risk of most medical conditions (except dyslipidemia) than the other quintiles.

Depression was similar in all groups, but slightly more prevalent in the most disadvantaged quintile. The prevalence of PTSD and traumatic brain injury ranged from 0.2% to 6.7%, with a lower prevalence in the most disadvantaged quintile of PTSD. No collinearity was demonstrated between education and ADI quintiles, or between household income and ADI quintiles.

Conclusion

Findings show that living in disadvantaged areas increases the risk of dementia among US VHA veterans. The results highlight the importance of societal exposure and vulnerability to dementia risk, even in the largest US National Integrated Health System.

Addressing social exposomes in research, advocacy, community-based care management, and policy is crucial, as they are a key factor linked to health inequalities.

Societal exposure controls such as the ADI help identify individuals at increased risk of developing ADRD and inform clinical practice.

Future research should focus on understanding the impact of the social exposome on longevity and implementing a life course approach to understand how social and environmental vulnerabilities in early, middle and late life affect brain health and eventual risk of ADRD.