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Circadian Rhythm Sleep dysregulation contributes to multiple illnesses and conditions. Examples of these are shift work sleep disorder, delayed sleep phase syndrome, jet lag, and Non-24-Hour Sleep-Wake Disorder (N24HSWD).
Non-24-Hour Sleep-Wake Disorder (N24HSWD)
Non-24-hour sleep-wake disorder mainly affects people who are totally blind and who don't have sensitivity to light. Without that light awareness, their circadian clocks will not reset, so their day may run slightly longer or shorter then 24-hours, causing a slight delay or advance in their body clock each day.
Once their circadian clock stops matching the 24-hour light-dark cycle, people who suffer from N24HSWD begin to have trouble going to sleep on a regular schedule. As their sleep-wake cycle moves gradually later and later-from 15 minutes to 1 hour each day--sleeping at night becomes more and more difficult, and their drive to sleep during the day increases.
Eventually, the person's sleep-wake cycle moves back into sync with the night, and they're able to sleep well during what is considered a conventional sleep period. But this is only temporary: the alignment between the internal circadian rhythm and the 24-hour light-dark cycle doesn't last an again the sleep cycle begins to shift.
It's estimated that 50% of totally blind people in the United States (approximately 65,000) have N24HSWD. This condition can also affect sighted people. However, cases are rarely reported in this population, and the true rate of N24HSWD in the general population is not known.
Shift Work Sleep Disorder (SWSD)
Shift work is used to describe regular employment outside of the normal "day work" hours. Human beings are diurnal creatures and it is biologically unnatural for them to work at night. Shift work can lead to potential impairments in work alertness and interfere with daytime sleep1. People who suffer from SWSD may experience insomnia and excessive sleepiness, which can significantly impact daily life.
Delayed Sleep Phase Syndrome (DSPS)
Delayed Sleep Phase Syndrome (DSPS) is characterized by sleep onset and wake times that are usually delayed 3 to 6 hours, relative to conventional sleep-wake times. The sufferer typically finds it difficult to initiate sleep before roughly 2 AM to 6 AM. People with DSPS prefer a wake time of 10 AM and 1 PM when they are free of societal constraints. Sleepiness is greatest in the morning and lessens as the circadian drive for wakefulness peaks in the late afternoon2.
Jet-Lag
Jet-Lag occurs when rapid travel across time zones leads to a mismatch or lack of synchrony between the activity of internal-rhythm generating systems and the local time cues, whether social or environmental. Those who experience Jet-Lag may experience symptoms such as daytime tiredness, inability to get to sleep at night (after an eastward flight) or early awakening (after a westward flight), disturbed nighttime sleep, impaired daytime alertness and performance, disorientation, gastrointestinal problems, loss of appetite, inappropriate timing of defecation, and excessive need to urinate during the night3.
References
- Kryger, Meir H, Thomas Roth, and William C. Dement. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia: Elsevier, 2005. p 673. Print.
- Kryger, Meir H, Thomas Roth, and William C. Dement. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia: Elsevier, 2005. p 692. Print.
- Kryger, Meir H, Thomas Roth, and William C. Dement. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia: Elsevier, 2005. p 659-660. Print.
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