Circadian rhythms disorders

The disturbances in the circadian rhythms are part of a separate sub-group of sleep disorders/sleep. They lead to a discrepancy between the time of the individual sleep and the circadian clock schedule. These conflicts occur due to a variety of external pressures or life habits and lead to fatigue, poor performance at work or school, and to a disturbed sleep - in particular to the problems to fall asleep or to wake up in desired time.

 

The main disorders of circadian rhythms and sleep

the night work

The individuals who work at night should perform their functions and duties at hours that differ from those favored by the circadian clock. This discrepancy contributes to a more low vigilance and performance on the job, to an increase in the risk of accidents, to the return (by car) to the house and to a inadequate sleep during the day.
After a quarter of night work, it may be that the workers are sleeping one to three hours less than if they had worked during a quarter day. By carefully choosing the quantity and the time of exposure to light and darkness, it is possible to assist the circadian clock to align with the hours of work and rest.

The time lag

Every year, millions of travelers suffer from jet lag after crossing quickly several time zones, thus causing a decline in their vigilance and their performance to their arrival. In practical terms, the circadian clock normally takes more time to reach the flight destination. The severity of the time lag depends on the direction of flight and the number of time zones crossed.

• Flights to the east is are associated with difficulties in falling asleep, to a disturbed sleep in the first half of the night, difficulties to wake up and a tired in the morning or early in the day.

• Flights to the west coast are associated with a decrease in the quality of sleep during the second half of the night, an early morning wake up and a fatigue in the late afternoon or evening.

The syndrome of the advanced sleep phase

It is more frequently observed in older individuals. It is characterized by a slumber in the evening, the tendency to bed early (between 18 h and 21 h) and to wake up early (between 1 h and 4 h of the morning).  The quality of sleep is usually normal if patients go to bed early, but the symptoms appear if they go to bed late.
The family syndrome in advance of sleep phase, which cause an extreme tendency to be a "morning bird" among several members of the family, was bound to a mutation of the "genes of the clock".  This observation supports the hypothesis that some disorders of circadian rhythms would be genetic.

The syndrome of the delayed sleep phase

It is characterized by a delay of the sleep episode main and by the inability to fall asleep or wake up to in desired hours. Those syndrome are of extreme layer-late who go to bed hungry between 3 h and 6 h and are waking up between 12 h and 15 h. The quality and duration of their sleep are normal if they lie down in hours that their body wants to. The symptoms appear when patients are trying to go to bed earlier to be able to wake up earlier. Their biological tendency to sleep is in conflict with the school schedule and the work schedules of day. This syndrome often emerges after puberty and is relatively common among adolescents and young adults.

The Syndrome cycle wake/sleep which does not last 24h

The patients suffering from this syndrome are asleep with one or two hours of divergence on that of the sleep every day. To drowsiness and disturbances of sleep appear the days or their natural rhythms are out of phase with the constraints of work and everyday life. The patients will have less difficulty to adapt during certain periods when their internal clock is synchronized to the hours of the normal society. This condition is rare in individuals with normal vision. The patients receiving non-lights stimulation at the level of the clock are more likely to suffer from this syndrome.

The causes of sleep disorders

There is not a factor of single cause related to disorders of circadian rhythms. However, the research can move forward that some of these disorders have a genetic basis. For example, the syndrome of the advanced family sleep phase, responsible for the trends "early riser" within the same family, may emerge genetic mutation.

Some other causes of disorders of circadian rhythms are:

• Bad medical conditions (neurological disease or cancer)
• Mood disorders such as depression and anxiety
• Schedule changes, such as night work