A circadian rhythm sleep disorder (CRSD) arises when either the person's body clock is disrupted or when it is misaligned to the external environment. This results in an impairment of biological rhythms that affects a person's desired work/study and daily life schedule. typically have disturbed sleep, which can be either
(a) Hypersomnia (excessive sleep), which affects their usual daily life, work or studies etc or
(b) Insomnia at night, resulting in daytime fatigue.
6 main types of CRSD have been described:
i. Delayed sleep phase disorder, more common in young people, where the person finds it difficult to fall asleep at a normal timing as well as to wake up at a normal timing.
ii. Advanced sleep phase disorder, more common in the elderly, where the person tends to go to sleep earlier and wake up much earlier compared to others.
iii. Irregular sleep-wake rhythm disorder, where a person suffers from fragmented and disorganized sleep over the 24 hours of the day, such as waking frequently in the night while also needing to take naps in the day. There is insufficient total sleep time, poor sleep efficiency and quality.
iv. Non-24-hour sleep-wake disorder, most common in blind people who are unable to detect light and hence develop long term sleep-wake patterns that are out of sync with the usual 24-hour light-dark environmental cycle.
v. Shift work sleep disorder, which affects people who work night shifts or have irregular working hours.
vi. Jet Lag: difficulty initiating or maintaining sleep, due to misalignment between the body clock and external environmental cues as a result of travel across many time zones.
