Sleep patterns change with aging, independent of other factors, and include advanced sleep timing, shortened nocturnal sleep duration, increased frequency of daytime naps, increased number of nocturnal awakenings and time spent awake during the night, and decreased slow wave sleep. Most of these changes seem to occur between young and middle adulthood; sleep parameters remain largely unchanged among healthy older adults. The circadian system and sleep homeostatic mechanisms become less robust with normal aging. The amount and pattern of sleep-related hormone secretion change as well. The causes of sleep disturbances in older adults are multifactorial.