[Sleep rhythm disturbances in Alzheimer's disease].

PURPOSE: Sleep-wake rhythm disturbances observed in Alzheimer's disease are correlated with the severity of cognitive impairment and often result in institutionalization. These disturbances are also a major cause of psychotropic medication misuse. We report age-related physiologic and disease related pathologic changes in sleep-wake rhythms and propose chronobiological treatment approaches in patients with Alzheimer's disease. CURRENT KNOWLEDGE AND KEY POINT: Alzheimer patients show a greater breakdown of the circadian sleep-wake cycle compared to similarly aged non demented controls. Demented patients spend their nights in a state of frequent restlessness and their days in a state of frequent sleepiness. These sleep-wake disturbances became increasingly more marked with progression of the disease. The architecture of sleep in Alzheimer's disease is marked by further decreases of slow wave sleep (SWS) and rapid eye movement (REM) sleep, and increases of time and frequency of awakening compared to age-matched control subjects. The sleep-wake disturbances in elderly people and particularly Alzheimer patients may result from changes at different levels: a reduction of environmental synchronizers or their perception, a lack of mental and physical activity, an age or disease related anatomical changes with loss of functionality of the biological clock(s). FUTURE PROSPECTS AND PROJECTS: In Alzheimer patients, controlling sleep-wake disturbances with sedative drugs often increases both sleep disturbance and cognitive dysfunction. A chronobiological approach with bright-light therapy, melatonin administration, restricted time in bed, and diurnal activity may be an interesting therapeutic alternative in the management of sleep-wake disorders in Alzheimer patients. The aim of these therapeutics is to improve sleep and diurnal activity and consequently to increase the quality of life in Alzheimer patients.