THE POTENTIAL FOR TREATING SLEEP DISORDERS

摘要

Circadian Rhythm Sleep Disorders (CRSD)are sleep problems that are associated with either a misalignment of the circadian clock with the 24 h day or an intrinsic property of the clock. Circadian misalignment can occur following an abrupt shift in external time, for example after rapid transmeridian travel, or when beginning night shift or early morning shift work. In addition, chronic circadian misalignment occurs in sufferers of advanced (ASPS) and delayed (DSPS) sleep phase insomnia, whose circadian rhythms are not aligned with the societal norm sleep schedules and thus have abnormally early or late bedtimes, respectively. The causes of ASPS and DSPS may be extrinsic, such as lighting at inappropriate times, or intrinsic, such as abnormal light sensitivity or aberrant clock timing or both. Recent evidence has suggested that polymorphisms in a number of human clock genes may be associated with ASPS (per 2) and DSPS (per 3). Another less common CRSD is non-24 h sleep/wake disorder where there is desynchronisation from the 24 h day. This is most frequently observed in totally blind people, although there are also some cases of free-running circadian rhythms reported in sighted people and in some dim light, long winter environments. Non-24 h sleep/wake disorder is cyclical in nature and is characterised by periods of good sleep (long duration nocturnal sleep with no daytime napping) followed by periods of poor sleep (short duration nocturnal sleep with daytime naps). This pattern of sleep follows the circadian clock as it runs in and out of synchrony with the 24 h day.