Remote Odor Memory in Alzheimer's Disease: Deficits as Measured by Familiarity

Deficit in olfaction and remote nonolfactory memory in Alzheimer's disease (AD) motivated the present study of remote memory for odors and faces, operationally defined as rated familiarity, in patients with AD and controls. Uncommon engineering symbols were rated for familiarity to ensure task comprehension. Results showed that patients with AD rate odors, but not faces, as significantly less familiar than do controls, which is indicative of deficit in remote odor memory. Follow-up testing 1 year later again showed this result. Poor odor-detection sensitivity in patients, with AD, but lack of significant correspondence between sensitivity and familiarity, suggests an existing but limited effect of sensitivity on familiarity. The findings provide further evidence that olfaction may be a useful modality for early identification of AD.