title: Episodic memory of odors stratifies Alzheimer biomarkers in normal elderly.
abstract: The objective of this study was to relate a novel test of identifying and recalling odor percepts to biomarkers of Alzheimer's disease (AD) in well-characterized elderly individuals, ranging from cognitively normal to demented.
  
  
  
  One hundred eighty-three participants (cognitively normal: n = 70; subjective cognitive concerns: n = 74; mild cognitive impairment [MCI]: n = 29, AD dementia: n = 10) were administered novel olfactory tests: the Odor Percept IDentification (OPID) and the Percepts of Odor Episodic Memory (POEM) tests. Univariate cross-sectional analyses of performance across diagnoses; logistic regression modeling, including covariates of age, sex, education, APOE genotype, and neuropsychological test scores; and linear mixed modeling of longitudinal cognitive scores were performed. Amyloid deposition and MRI volumetrics were analyzed in a subset of participants.
  
  
  
  Accuracy of identification and episodic memory of odor percepts differed significantly across diagnosis and age, with progressively worse performance across degrees of impairment. Among the participants who were cognitively normal or had subjective cognitive concerns, poorer than expected performance on the POEM test (based on the same individual's performance on the OPID and odor discrimination tests) was associated with higher frequencies of the APOE ε4 allele, thinner entorhinal cortices, and worse longitudinal trajectory of Logical Memory scores.
  
  
  
  Selective impairment of episodic memory of odor percepts, relative to identification and discrimination of odor percepts revealed by this novel POEM battery, is associated with biomarkers of AD in a well-characterized pre-MCI population. These affordable, noninvasive olfactory tests offer potential to identify clinically normal individuals who have greater likelihood of future cognitive decline. Ann Neurol 2016;80:846-857.
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.|Department of Psychology, Endicott College, Beverly, MA.
authors.forename: Alefiya
authors.initials: A
authors.lastname: Dhilla Albers
authors.affiliation: Department of Biostatistics, School of Nursing, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Josephine
authors.initials: J
authors.lastname: Asafu-Adjei
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Mary K
authors.initials: MK
authors.lastname: Delaney
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: Kelly
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Gomez-Isla
authors.affiliation: Department of Psychiatry, Massachusetts General Hospital, Boston, MA.
authors.forename: Deborah
authors.initials: D
authors.lastname: Blacker
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Boston, MA.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Johnson
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Reisa A
authors.initials: RA
authors.lastname: Sperling
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Hyman
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, MA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Betensky
authors.affiliation: Osmic Enterprises, Cincinnati, OH.
authors.forename: Lloyd
authors.initials: L
authors.lastname: Hastings
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Albers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000235:genetics / Q000473:pathology / Q000523:psychology*; D053327:Apolipoprotein E4 / Q000235:genetics*; D001284:Atrophy / Q000473:pathology; D015415:Biomarkers; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000235:genetics / Q000473:pathology / Q000523:psychology*; D003430:Cross-Sectional Studies; D018728:Entorhinal Cortex / Q000473:pathology; D005260:Female; D006624:Hippocampus / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D061212:Memory, Episodic; D059906:Neuroimaging; D009483:Neuropsychological Tests; D055696:Olfactory Perception; D058225:Plaque, Amyloid / Q000473:pathology*; D000072078:Positron Emission Tomography Computed Tomography
chemical_list: D053327:Apolipoprotein E4; D015415:Biomarkers