Cerebrovascular disease is associated with memory function in the Health and Aging in Africa Longitudinal Study of an INDEPTH community in rural South Africa

Abstract

AbstractBackgroundHealth and Aging in Africa Longitudinal Study of an INDEPTH community in South Africa (HAALSI) is a sister study to the US‐based Health and Retirement Study. The purpose of HAALSI is to characterize the social, economic, biological, physical, and mental health factors in a population‐representative cohort of older adults in a rural community in Agincourt, South Africa. Beginning in 2020, as part of an Alzheimer’s disease and related disorders (ADRD) substudy, we conducted neuropsychological evaluations and structural magnetic resonance imaging (MRI) in a subset of HAALSI participants. Here, we report preliminary observations on the relationship of white matter hyperintensity (WMH) volume, a marker of small vessel cerebrovascular disease, and hippocampal volume, a marker of neurodegeneration, on memory function in a group of substudy participants.MethodNinety‐nine HAALSI ADRD participants with available MRI scans and neuropsychological outcomes at time of analysis (mean ± SD; age = 70.3 ± 10.9, 87% with no formal education or some primary education) were included in these analyses. Participants received research‐grade, harmonized 1.5T MRI scanning at a private hospital and were evaluated with a battery of neuropsychological tests. Using in‐house developed software and FreeSurfer, respectively, we derived total WMH volume and total hippocampal volume. We examined the association of these variables with memory function, operationalized as the delayed recall score of the Logical Memory Test, adapted for context.ResultAdjusting for education level, increased WMH volume was associated with poorer performance on the Logical Memory Test (standardized β = ‐0.21, p<0.05) but hippocampal volume was not (standardized β = 0.09, p = 0.41). Associations of these MRI markers with memory function did not interact with education level.ConclusionIn these preliminary analyses of older adults in a rural South African community, markers of small vessel cerebrovascular disease but not neurodegeneration are associated with poorer cognitive outcomes. Future work will examine the pathways that give rise to cognitive impairment and dementia in this rural South African population and track cognitive trajectories over time.