Olfactory identification deficits and MCI in a multi-ethnic elderly community sample

Odor identification deficits occur in Alzheimer's disease (AD) and mild cognitive impairment (MCI), and predict clinical conversion from MCI to AD. In an epidemiologic study conducted in a multi-ethnic community elderly sample (average 80 years old), the University of Pennsylvania Smell Identification Test (UPSIT, range 0-40) was administered to 1092 non-demented subjects. Women (mean 26.6, S.D. 6.6) scored higher than men (mean 24.4, S.D. 7.4, p<.02), and ethnic differences were not significant after controlling for age and education. UPSIT scores correlated inversely with age (r=-0.24, p<.0001) and positively with Selective Reminding Test immediate recall (r=0.33), delayed recall (r=0.28), category fluency (r=0.28) and the 15-item Boston Naming Test (r=0.23), all ps<.0001. In a sub-sample in which MRI was done, UPSIT scores showed a significant correlation with hippocampal volume (n=571, r=0.16, p<.001) but not entorhinal cortex volume nor total number of white matter hyperintensities. In ANOVA, UPSIT scores differed (p<.0001) as a function of MCI classification: no MCI (mean 26.6, S.D. 6.8), non-amnestic MCI (mean 24.4, S.D. 7.2), and amnestic MCI (mean 23.5, S.D. 6.7). The difference between amnestic MCI and no MCI remained significant after controlling for relevant covariates. These findings indicate that the predictive utility of olfactory identification deficits for decline from no MCI to MCI and AD needs to be assessed in longitudinal studies of elderly community samples.