Age-related changes in circadian rhythm (e.g., fragmented sleep-wake patterns) occur in many older persons but are particularly pronounced in patients with Alzheimer's disease. In these patients, disruptions of circadian rhythms can be severe enough to increase mental decline, agitation during the day, and restlessness at night. Moreover, patients whose nocturnal restlessness disrupts the sleep of the caregiver are more likely to be institutionalized than those who have cognitive impairment alone.