Symptoms of abnormally early sleep are common in the elderly. Aging is associated with earlier habitual bedtimes and earlier morning wake-up times. Intrinsic disorders, are those in which the endogenous circadian regulation of sleep is itself abnormal. These intrinsic disorders include irregular sleep-wake rhythm, free-running disorder, and delayed sleep phase syndrome (DSPS), as well as advanced sleep phase syndrome (ASPS). Amplitudes of other circadian rhythms, including core body temperature, are also reduced with age, and post-mortem brain studies have revealed reductions in suprachiasmatic nucleus (SCN) volume, cell number, and neuropeptide rhythms, suggesting an age-related clock defect. Treatments recommended for ASPS include chronotherapy, timed melatonin administration, and timed light exposure. These treatments are all directed towards the primary goal in treating ASPS: to correct the abnormally early timing of sleep by delaying the circadian clock.