Association Between Hippocampal Volume and African Neuropsychology Memory Tests in Adult Individuals with Probable Alzheimer's Disease in Democratic Republic of Congo.

BACKGROUND: Western studies indicate potential associations between hippocampal volume and memory in the trajectory of Alzheimer's disease (AD). However, limited availability of neuroimaging technology and neuropsychological tests appropriate for sub-Saharan African (SSA) countries makes it difficult to establish neuroanatomical associations of hippocampus and memory in this locale. OBJECTIVE: This study examined hippocampal volumes and memory in healthy control (HC) and probable AD groups in the Democratic Republic of Congo (DRC). METHODS: Forty-six subjects with probable AD and 29 HC subjects were screened using the Community Instrument for Dementia and the Alzheimer Questionnaire. Participants underwent neuroimaging in Kinshasa, DRC, and memory was evaluated using the African Neuropsychology Battery (ANB). Multiple linear regression was used to determine associations between hippocampal volumes and memory. RESULTS: Patients with probable AD performed significantly worse than HCs on ANB memory measures, and exhibited greater cerebral atrophy, which was significantly pronounced in the medial temporal lobe region (hippocampus, entorhinal cortex). Both AD and HC subjects exhibited high rates of white matter hyperintensities compared to international base rate prevalence, which was significantly worse for probable AD. Both also exhibited elevated rates of microhemorrhages. Regression analysis demonstrated a significant association between hippocampal volume and ANB memory tests. Hippocampal atrophy discriminated probable AD from the HC group. CONCLUSIONS: This study establishes the feasibility of conducting neuroimaging research in the SSA, demonstrates many known neuroimaging findings in probable AD patients hold up using culturally appropriate memory tasks, and suggest cardiovascular problems are a greater issue in SSA than in Western countries.

The Reliability of the African Neuropsychology Battery in Persons of African Descent.

OBJECTIVE: The African Neuropsychology Battery (ANB) includes eight culturally appropriate cognitive tests developed for use in the Congo and other sub-Saharan African populations. The current study examines the reliability of the ANB in three samples of participants of African descent. METHODS: Subjects were recruited in the United States and the Congo to participate in three studies of ANB internal consistency reliability (Study 1), test-retest reliability (Study 2), and interrater reliability for the two ANB measures (i.e., Visuospatial Memory and Proverb Tests) requiring examiner ratings of response adequacy (Study 3). Subjects were administered ANB tests of visuospatial perception, language, memory, abstract reasoning, and problem solving. We calculated Cronbach's alpha, corrected item-total correlations and mean inter-item correlations for internal consistency, Pearson product-moment correlations and intraclass correlation coefficients for test-retest reliability, and intraclass correlation coefficients for interrater reliability. RESULTS: The ANB tests had acceptable internal consistency (Cronbach's alphas ranging from .37 to .93). Across subtests, test-retest reliability coefficients ranged from .39 to .91, and intraclass correlation stability coefficients (ICCs) ranged from .39 to .82. Of the two ANB tests requiring interrater reliability, only the Proverb Test had a low ICC of .13, (confidence intervals: -.29 to .52). CONCLUSION: The present study demonstrated that most ANB tests show adequate reliability in participants of African descent. However, the scoring criteria of the African Proverb Test require revision in order to improve the interrater reliability of the measure.