Sleep disturbances, specifically early morning awakenings, insomnia, and increased daytime napping, show higher prevalence with advanced age. Age-related circadian changes are seen at all levels, from molecular and cellular within the SCN to physiologic, hormonal, and behavioral output of the circadian clock. Modifications in circadian rhythms alone do not fully explain common age-related difficulties, such as advanced sleep phase or the decrease in the amplitude of the sleep-wake activity cycle. It is likely that changes in both circadian and sleep homeostatic processes, or the interaction between the two, are responsible for the impaired sleep of older adults. Although age-related changes have been reported in healthy "usual" older adults, evidence suggests that, in addition to age, health status, medications, social structure, and physical environment are perhaps even more important contributors to the high prevalence of circadian-related sleep disturbances. As Ohayon and coworkers  noted...the aging process per se is not responsible for the increase of insomnia often reported in older people. Instead, inactivity, dissatisfaction with social life, and the presence of organic diseases and mental disorders were the best predictors of insomnia, age being insignificant. Healthy older people (i.e., without organic or mental pathologies) have a prevalence of insomnia symptoms similar to that observed in younger people. Increasing evidence suggests that alterations in the circadian system, which are evident later in life, may begin to appear during the middle years and that this is the time to begin to take measures to prevent or delay their onset. Advances in understanding of the circadian system and its interactions with sleep have resulted in some promising treatment options. Interventions that target the circadian system, such as selective application of bright light, structuring daily activities, increased exercise, and in some studies administration of melatonin, have been shown to improve circadian rhythm-based sleep disorders.