The purpose of this study is to determine the effects of the anticholinesterase drug donepezil on sleep in Alzheimer disease patients. Sleep structure and respiratory parameters will be analyzed by polysomnography.

Central acting cholinesterase inhibitors are the first primary pharmacological treatment approved for Alzheimer disease, of which donepezil is the most frequently used. Multicenter studies have found little toxicity, and its side effects (diarrhea, nausea, vomiting, nightmares, among others) are mild and transient. According to the literature, cholinergic active drugs may be expected to affect REM (rapid eye movement) sleep. Another possible effect is related to respiratory parameters in patients with Alzheimer disease and obstructive sleep apnea. In fact, cholinergic activity influences the upper airway opening via central and peripheral mechanisms.

Intervention: Patients will be administered donepezil or placebo. The study has a randomized, double-blind placebo-controlled design. Complete polysomnography with REM sleep EEG spectral analysis and ADAS-cog scoring will be performed at baseline and after 3 and 6 months.

Inclusion Criteria:

• Diagnosis of Alzheimer's disease based on the probability criteria of the Alzheimer's Disease and Related Disorders Association
• Rated 1 and 2 (mild to moderate level) on the Brazilian version of the Clinical Dementia Rating

Exclusion Criteria:

• Other causes of dementia
• Other severe medical or psychiatric disease
• Clinical indication of psychoactive drugs other than experimental drug