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AMSTERDAM -- Significant differences in dementia incidence emerged based on neighborhood deprivation, a study of 1.6 million U.S. veterans showed.

Over a mean follow-up of 11 years, older veterans in the most socioeconomically disadvantaged areas were 22% more likely to develop dementia than those in the least disadvantaged neighborhoods (adjusted HR 1.22, 95% CI 1.21-1.24), reported Christina Dintica, PhD, of the University of California San Francisco, in a poster presented at the annual Alzheimer's Association International Conference.

The study, simultaneously published in , is the largest of its kind ever conducted, Dintica told MedPage Today.

Increased risk wasn't seen just when comparing areas at opposite ends of the socioeconomic scale, she pointed out. Dementia incidence was inversely correlated with socioeconomic advantage consistently across neighborhoods. And while the study didn't analyze potential drivers of the association, the negative health consequences of living in an economically challenged area are well-documented, Dintica said.

"People living in disadvantaged neighborhoods tend to face more life stressors and have fewer resources," she noted. "These factors have all been linked to adverse health outcomes and less capacity to cope with these effects. This might explain the higher risk of dementia that we saw."

The investigators drew on the national Veterans Health Administration (VHA) healthcare database to build the cohort. For every year from 1999-2021, they extracted a random sample of 5% of veterans 55 or older who had received VHA healthcare, then merged these samples and selected those who were free of an Alzheimer's disease or dementia diagnosis at baseline.

Using 9-digit zip codes, the investigators linked each veteran's residential location to the national (ADI). This tool contains composite measures of neighborhoods integrating several social determinants of health, including the average education level of local residents, employment and housing data, and poverty levels. The team divided ADI data into quintiles, with the first quintile being the least deprived and the fifth quintile the most deprived.

The sample included 1,637,484 veterans with full diagnostic and ADI data. At baseline, the cohort had a mean age of 68.6 years; 98% were men. Most (86.9%) were white, 9.3% were Black, and the remainder were Hispanic (0.6%), Asian (0.4%), or of unknown race or ethnicity (2.8%).

Demographics and medical comorbidities varied by quintile. Black veterans were most likely to live in the fifth (most disadvantaged) quintile. Cardiovascular risk factors were common in all quintiles, but were more common in the more disadvantaged areas. For example, tobacco use was lowest in the first quintile and highest in the fifth (8.5% vs 17.2%). A similar trend was seen with diabetes (20.9% vs 26.5%), obesity (14.4% vs 17.2%), and hypertension (61.1% vs 68.4%). The prevalence of depression was similar among the groups (11.8% to 12.9%), as was traumatic brain injury and post-traumatic stress disorder.

Veterans were followed until they had a dementia diagnosis, died, or had their last medical encounter. Over a median of 11.2 years, dementia developed in 12.8% of the sample (208,909 participants). The fully adjusted model accounted for sex, race and ethnicity, traumatic brain injury, post-traumatic stress disorder, depression, current tobacco use, diabetes, obesity, hypertension, dyslipidemia, education, and income.

Compared with individuals residing in the first or least-disadvantaged quintile, adjusted HRs were 1.09 (95% CI 1.07-1.10) for those in the second quintile, 1.14 (95% CI 1.12-1.15) for those in the third quintile, 1.16 (95% CI 1.14-1.18) for those in the fourth quintile, and 1.22 (95% CI 1.21-1.24) for those in the fifth or most-disadvantaged quintile. Repeating the analysis using competing risk for mortality produced similar results.

The findings are consistent with other studies of socioeconomic environment and health, noted Claire Sexton, DPhil, senior director of scientific programs and outreach at the Alzheimer's Association, which partially funded the study.

"Living in the poorest neighborhoods is associated with a higher risk for brain changes related to Alzheimer's disease, such as build-up of amyloid," Sexton told MedPage Today. "These links may be mediated by other risk factors for dementia. For example, area deprivation has been associated with poor nutrition, low levels of physical activity, sleep disruption, and higher levels of air pollution, all of which have, in turn, been associated with an increased dementia risk."

The study carries a message for clinicians, the researchers noted -- that a patient's everyday environment, or "social exposome," may play a role in brain health. Theoretically, veterans enrolled in the VHA have equal access to care; however, this study indicates that health inequalities persisted in disadvantaged areas, they observed.

"When the patient is seen in the clinic, it may be relevant to have a conversation about the resources available to the patient, as well as what kind of network of social support they have, particularly in regard to managing health conditions related to dementia risk," Dintica said.

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