The utility of olfactory function in distinguishing early-stage Alzheimer's disease from HIV-associated neurocognitive disorders

Objectives: Given the rising number of older people with HIV (PWH) and the overlap in cognitive dysfunction profiles in HIV-associated neurocognitive disorders (HAND) and Alzheimer's disease and its precursor, amnestic mild cognitive impairment (aMCI), methods are needed to distinguish aMCI/Alzheimer's disease from HAND. As an early indicator of Alzheimer's disease, we examined whether olfactory dysfunction could help to distinguish between aMCI/Alzheimer's disease and HAND among PWH. Design: An observational cohort study. Methods: Eighty-one older (>= 50 years) PWH (83% men, 65% white) from the California NeuroAIDS Tissue Consortium completed the University of Pennsylvania Smell Identification Test (UPSIT; higher scores = better smell identification) and a comprehensive seven-domain neuropsychological test battery and neuromedical evaluation. HAND was classified via Frascati criteria. High aMCI risk was defined as impairment (>1.0 SD below normative mean) on two of four delayed recall or recognition outcomes (at least one recognition impairment required) from the Hopkins Verbal Learning Test-Revised and the Brief Visuospatial Memory Test-Revised. We examined UPSIT scores in relation to aMCI risk and HAND status, and continuous memory scores considering adjustments for demographics and relevant clinical or HIV disease characteristics. Results: Fifty-seven participants were classified with HAND (70%) and 35 participants were classified as high aMCI risk (43%). UPSIT scores were lower (worse) in the high versus low aMCI risk group [F (1,76) = 10.04, P = 0.002], but did not differ by HAND status [F (1,76) = 0.62, P = 0.43]. UPSIT scores positively correlated with all memory outcomes (Ps < 0.05). Conclusion: Olfactory assessments may help in detecting early aMCI/Alzheimer's disease among PWH and allow for appropriate and early disease intervention.