Disturbed sleep is a major clinical problem in Alzheimer's disease (AD). Apolipoprotein epsilon4 (APOE epsilon4) carrier status may increase risk of AD, yet there are no data on relations between APOE status and progression of sleep disturbance in AD. The objective of this study was to determine if sleep parameters in AD patients change over time as a function of APOE carrier status. Forty-four community-dwelling AD patients with diagnosis of probable AD were followed from early stages of disease. Their sleep/wake parameters were compared according to APOE status. For APOE epsilon4 carriers, only wake after sleep onset (WASO) increased in association with lower cognitive function as indicated by the Mini-Mental State Examination (MMSE); for non-epsilon4 subjects, increases in WASO and declines in total sleep time, sleep efficiency, and the amplitude of the rest/activity circadian rhythm over time were associated with lower performance on the MMSE. In these data, APOE status was associated with the progression of sleep/wake disturbances in AD. Overall, there was greater deterioration on sleep parameters in patients negative for the epsilon4 allele.