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Original Investigation
January 6, 2020

Association of Neighborhood-Level Disadvantage With Cerebral and Hippocampal Volume

Author Affiliations
  • 1Wisconsin Alzheimer’s Disease Research Center, University of Wisconsin School of Medicine and Public Health, Madison
  • 2Health Services and Care Research Program, University of Wisconsin School of Medicine and Public Health, Madison
  • 3Department of Psychology, University of Southern California, Los Angeles
  • 4Wisconsin Alzheimer’s Institute, University of Wisconsin School of Medicine and Public Health, Madison
  • 5Wisconsin Center for Education Research, University of Wisconsin-Madison
  • 6Department of Biostatistics and Medical Informatics, School of Medicine and Public Health, University of Wisconsin-Madison
  • 7Department of Neurosciences, University of California, San Diego
  • 8Geriatrics Division, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison
  • 9Geriatric Research Education and Clinical Center, William S. Middleton Hospital Department of Veterans Affairs, Madison, Wisconsin
JAMA Neurol. Published online January 6, 2020. doi:10.1001/jamaneurol.2019.4501
Key Points

Question  Is neighborhood socioeconomic disadvantage associated with hippocampal and total brain volume in a cognitively unimpaired population?

Findings  In this cross-sectional study of 951 cognitively unimpaired individuals, living in the most socioeconomically disadvantaged neighborhoods was associated with significantly lower hippocampal and total brain tissue volume, adjusted for premorbid brain volume. Increased cardiovascular risk mediated the association with total brain tissue but not hippocampal volume.

Meaning  Neighborhood disadvantage may be associated with brain tissue volume during the aging process in the absence of clinical cognitive impairment.

Abstract

Importance  Identifying risk factors for brain atrophy during the aging process can help direct new preventive approaches for dementia and cognitive decline. The association of neighborhood socioeconomic disadvantage with brain volume in this context is not well known.

Objective  To test whether neighborhood-level socioeconomic disadvantage is associated with decreased brain volume in a cognitively unimpaired population enriched for Alzheimer disease risk.

Design, Setting, and Participants  This study, conducted from January 6, 2010, to January 17, 2019, at an academic research neuroimaging center, used cross-sectional data on 951 participants from 2 large, ongoing cohort studies of Alzheimer disease (Wisconsin Registry for Alzheimer’s Prevention and Wisconsin Alzheimer’s Disease Research Center clinical cohort). Participants were cognitively unimpaired based on National Institute on Aging–Alzheimer’s Association workgroup diagnostic criteria for mild cognitive impairment and Alzheimer disease, confirmed through a consensus diagnosis panel. The cohort was enriched for Alzheimer disease risk based on family history of dementia. Statistical analysis was performed from April 3 to September 27, 2019.

Main Outcomes and Measures  The Area Deprivation Index, a geospatially determined index of neighborhood-level disadvantage, and cardiovascular disease risk indices were calculated for each participant. Linear regression models were fitted to test associations between relative neighborhood-level disadvantage (highest 20% based on state of residence) and hippocampal and total brain tissue volume, as assessed by magnetic resonance imaging.

Results  In the primary analysis of 951 participants (637 women [67.0%]; mean [SD] age, 63.9 [8.1] years), living in the 20% most disadvantaged neighborhoods was associated with 4.1% lower hippocampal volume (β = −317.44; 95% CI, −543.32 to −91.56; P = .006) and 2.0% lower total brain tissue volume (β = −20 959.67; 95% CI, −37 611.92 to −4307.43; P = .01), after controlling for intracranial volume, individual-level educational attainment, age, and sex. Robust propensity score–matched analyses determined that this association was not due to racial/ethnic or demographic characteristics. Cardiovascular risk score, examined in a subsample of 893 participants, mediated this association for total brain tissue but not for hippocampal volume.

Conclusions and Relevance  For cognitively unimpaired individuals, living in the most disadvantaged neighborhoods was associated with significantly lower cerebral volumes, after controlling for maximal premorbid (total intracranial) volume. This finding suggests an association of community socioeconomic context, distinct from individual-level socioeconomic status, with brain volume during aging. Cardiovascular risk mediated this association for total brain tissue volume but not for hippocampal volume, suggesting that neighborhood-level disadvantage may be associated with these 2 outcomes via distinct biological pathways.

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