Olfactory Deficits and Donepezil Treatment in Cognitively Impaired Elderly

Donepezil 5mg will be given for 4 weeks and if tolerated, the dose will be increased to 10 mg per day. The dose range of 5 to 10 mg of donepezil per day will be continued for the study duration, and this is the recommended dose for donepezil in the treatment of mild to moderate Alzheimer's disease. For patients who do not tolerate donepezil or have a history of intolerance to donepezil or cannot take donepezil for other reasons, treatment with other cholinesterase inhibitors (galantamine or rivastigmine) is permitted at any stage of the protocol. Data will be analyzed in two ways: for donepezil alone, and for any cholinesterase inhibitor (donepezil or rivastigmine or galantamine) as the intervention.