Alzheimer's disease and related syndromes (AD) is a disease affecting memory but also the relationship with the environment and empower people. Patients with AD present in 90% of cases of behavioral disorders and of these behavioral disorders include agitation, apathy but also sleep disorders by circadian rhythm impairment.. No study has shown proven efficacy on the behavior of patients with AD. The main objective of the study was to assess the influence of environmental light nighttime sleep of residents.