Validation of olfactory deficit as a biomarker of Alzheimer disease.

Background: We evaluated smell identification as a biomarker for Alzheimer disease (AD) by assessing its utility in differentiating normal aging from an amnestic disorder and determining its predictive value for conversion from amnestic mild cognitive impairment (aMCI) to AD.

Methods: Cross-sectional study (AD = 262, aMCI = 110, controls = 194) measuring smell identification (University of Pennsylvania Smell Identification Test [UPSIT]) and cognitive status was performed, as well as longitudinal analysis of aMCI participants (n = 96) with at least 1 year follow-up (mean 477.6 ± 223.

Odor identification deficit in mild cognitive impairment and Alzheimer's disease is associated with hippocampal and deep gray matter atrophy.

Even in early stages, Alzheimer's disease (AD) is associated with olfactory deficit. We assess the association of volumetric differences in subcortical deep gray matter (DGM) structures and odor identification deficit (OID) in subjects with amnestic mild cognitive impairment (aMCI), AD and normal controls (NCs), and relate findings to the current gold standard right sided memory measure, visual reproduction. Eighty subjects (19 aMCI; 42 CE; 19 NC) were included in this study.