BACKGROUND: Anticholinergic challenge can induce odor identification impairment that indicates Alzheimer's disease pathology.

OBJECTIVE: To determine if decline in odor identification ability with anticholinergic challenge can predict improvement with donepezil, a cholinesterase inhibitor (ChEI), in patients with mild cognitive impairment (MCI).

METHODS: At baseline, the University of Pennsylvania Smell identification Test (UPSIT) was administered before and after an anticholinergic atropine nasal spray challenge. Donepezil was started at 5 mg daily, increased to 10 mg daily if tolerated, and then the dose was kept constant for 52 weeks. Main outcomes were change in Selective Reminding Test (SRT) total immediate recall and ADAS-Cog total score from baseline to 26 and 52 weeks.

RESULTS: In 37 participants, mean age 70.4 (SD 9.8) y, greater atropine-induced decrease in UPSIT score at baseline was associated with greater improvement in SRT total recall score from baseline to 26 and 52 weeks (p 

CONCLUSIONS: Anticholinergic challenge-induced odor identification decline was associated with cognitive improvement, and short-term improvement in odor identification tended to predict longer term cognitive improvement. These simple inexpensive strategies have the potential to improve selection of patients with MCI for ChEI treatment.