Olfactory Deficits and Donepezil Treatment in Cognitively Impaired Elderly

Olfactory identification deficits occur in patients with Alzheimer's disease (AD), are associated with disease severity, predict conversion from mild cognitive impairment (MCI) to AD and are associated with healthy elderly subjects developing MCI. Odor (olfactory) identification deficits may reflect degeneration of cholinergic inputs to the olfactory bulb and other olfactory brain regions. Acetylcholinesterase inhibitors (ACheI) like donepezil show modest effects in improving cognition but can be associated with adverse effects and increased burden and costs because of the need for prolonged, often lifelong, treatment. Converging findings on odor identification test performance (UPSIT, scratch and sniff 40-item test) from four pilot studies, including two of our own, suggest that acute change in the UPSIT in response to an anticholinergic challenge (atropine nasal spray), incremental change over 8 weeks, and even the baseline UPSIT score by itself, may predict cognitive improvement with ACheI treatment in MCI and AD. If change in odor identification deficits can help to identify which patients should receive ACheI treatment, this simple inexpensive approach will advance the goal of improving personalized treatment, improve selection and monitoring of patients for ACheI treatment, reduce needless ACheI exposure with risk of side effects, and decrease health care costs.