Our biological clock, located in the hypothalamus, is modulated according to external cues such as the light-dark cycle (the main factor in the synchronization of the environment and the clock), the work and leisure schedule. Thus, our biological clock works in collaboration with the external environment. Sometimes, the clock can dysfunction or fall out of sync with environmental rhythms and trigger the following disorders:

Delayed sleep phase syndrome (DSPS)
and advanced sleep phase syndrome (ASPS)

DSPS is the most common circadian rhythm sleep disorder. People with DSPS fall asleep late and rise late. This sleep disorder affects adolescents and young adults. In order to meet social demands, people with this sleep disorder go to bed late, but get up early, resulting in a lack of sleep that could possibly explain academic failures, automobile accidents and relationship problems. The exact prevalence of this syndrome is currently unknown.

ASPS refers to the internal clock that tend to move bedtime earlier in the evening. This sleep disorder is very rare. (It would seem that the biological clock has a natural tendency to delay sleep onset and not to advance it.) People with ASPS feel the need to go to bed very early in the evening (around 7 p.m.) and then wake up feeling rested in the middle of the night (around 2-3 a.m.). These people sleep an average of 7-8 hours a night. Just like in delayed sleep phase syndrome, the sleep is sufficient in length, but incompatible with social life.

Shift work or jet lag

Working a night shift compromises the sleep-wake cycle since the biological clock is no longer in agreement with the light-dark cycle. The biological clock sends a strong signal in an attempt to keep the person awake during the day. Consequently, night shift workers, whose schedules are the opposite of the biological clock, find themselves with problems in terms of alertness, concentration and memory. Obviously, this causes all kinds of mistakes, automobile accidents and even relationship problems.

Similar symptoms may also arise when or after travelling through several time zones. These sleep difficulties usually disappear after a few days, once the biological clock has adjusted to the new time zone.

How are circadian rhythm sleep disorders treated?
Can we adjust our biological clock?

Experimental treatments have shown that stimulants (caffeine), pharmacological medication, melatonin, phototherapy (exposure to bright light) and chronotherapy may help set our biological clock, thus eliminating or alleviating circadian rhythm sleep disorders. However, good sleep hygiene is still the best treatment, especially the good habit of sleeping in a dark and quiet room.

For those who work shifts, slightly adjusting your sleep schedule may help you adapt to your work schedule. For example, a few days before starting your shift, gradually delay the time you go to bed and wake up. That way, the night before your shift, you will already be more “adjusted” to your schedule, and accordingly, less tired and drowsy.

For those who travel a lot, planning a nap at a specific time may help you “adjust” your biological clock to the local time in the country you are visiting.

In some cases, a “non-adjusted” sleep schedule can explain underlying depression or simply poor sleep habits.

Consult your physician to find the right treatment for your condition.

Signs of DSPS

Impossibility of waking up at the normal time.
Deviation of a child or adolescent’s sleeping pattern, i.e. trouble waking up in the morning and falling asleep before the wee hours of the morning. These are not signs of laziness or disobedience. Children or teenagers with chronic problems waking up in the morning may have a biological clock that is out of sync with the environment.

References:

Dumont, M. “Le travailleur de nuit : donnez-lui l’heure juste.” Le Clinicien. (1999): 124-137.

American Academy of Sleep Medicine. International Classification of Sleep Disorders: Diagnostic and Coding Manual, 2nd ed. Rochester, 2005.

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