Circadian Rhythm
Circadian Rhythm
The circadian rhythm is largely independent of external factors that could indicate the respective time of day, night or even season. It serves to be able to orient oneself to time and to carry out periodically performed activities, such as sleeping, feeding, hibernation, reproduction, etc., in a relatively constant rhythm. Due to the changing length of the day - as a result of the change of seasons - a constant resynchronization of the internal clock is necessary. Nowadays, however, the circadian rhythm often has to be resynchronized at very short notice due to a rapid change in geographical location, such as after a transatlantic flight. The consequence of an initial lack of synchronization is the well-known jet-lag.
This group of diseases is characterized by a lack of synchronization of the intrinsic circadian rhythm with the light-dark alternation. Either the intrinsic pacemaker itself is disturbed or the sleep-wake rhythm deviates from a normal intrinsic circadian rhythm due to external factors.
Insomnia (difficulty falling asleep or staying asleep) or hypersomnia (constant insomnia), or both, are the result. If the affected person is able to align his or her sleep times with his or her internal rhythm, sleep duration and quality are normal, as is performance during the waking phase. Sleep disturbance is most common in shift work, with negative health effects and limited performance at work. Sleep diaries are the basis of diagnosis, and strict adherence to fixed bedtimes in conjunction with light therapy is the basis of therapy.
Healthy maintenance of the circadian rhythm
Although we don't have complete control over our circadian rhythms, there are tips for healthy sleep that we can use to try to better manage our 24-hour sleep cycles
- Provide sunshine: exposure to natural light, especially early in the day, helps reinforce the strongest circadian cue.
- Follow a consistent sleep schedule: Varying your bedtime or morning wake-up time can interfere with your body's ability to adjust to a stable circadian rhythm.
- Move daily: activity during the day can support your internal clock and help you fall asleep easier at night.
- Avoid caffeine: Stimulants like caffeine can keep you awake and upset the natural balance between sleep and wakefulness. Everyone is different, but if you have trouble sleeping, avoid caffeine after noon.
- Limit the amount of light before bed: Exposure to artificial light at night can disrupt circadian rhythms. Experts advise dimming lights and putting away electronic devices before bed, keeping them out of the bedroom and away from the sleeping surface.
- Keep naps short and early in the afternoon: Late and long naps can push bedtime back and throw your sleep rhythm off balance.
These steps to improve sleep hygiene can be an important part of supporting a healthy circadian rhythm, but other steps may be necessary depending on the situation. If you have persistent or severe sleep problems, daytime sleepiness, and/or a problematic sleep rhythm, it's important to talk to a doctor who can best diagnose the cause and offer the most appropriate treatment.
Disorders of the circadian rhythm
In circadian rhythm disorders, the endogenous sleep-wake rhythm (internal clock) and the external light-dark cycle run in an offset manner (desynchronization). The cause may be endogenous (e.g., delayed or advanced sleep phase syndrome) or external (e.g., jet lag, shift work).
If the cause is external, other circadian rhythms in the body, incl. temperature and hormone secretion, may become asynchronous with the light-dark cycle (external desynchronization) and with each other (internal desynchronization); in addition to insomnia and excessive sleepiness, these changes may lead to nausea, malaise, irritability, and depression.
The risk of cardiovascular disease and metabolic disorders may also be increased. It is particularly difficult to adjust to repeated circadian shifts (e.g., due to frequent long-distance travel or rotating shift work), especially when shifts change in counterclockwise direction. Counterclockwise shifts are those that move waking and sleeping times forward (e.g., flying east, rotating shifts from day to night to evening). Symptoms subside after a few days or, in some patients (e.g., the elderly), after a few weeks or months, while rhythms readjust.
Because light is a powerful synchronizer of circadian rhythms, exposure to bright light (sunlight or artificial light with an intensity of 5000-10,000 lux) after the desired wake-up time and the use of sunglasses before the desired bedtime accelerate readjustment.
Patients with circadian rhythm disorders often abuse alcohol, hypnotics, and stimulants.
Effects of a disturbed rhythm
When the circadian rhythm is disturbed, it means that the body's systems are not functioning optimally.
A disrupted circadian sleep-wake rhythm can lead to serious sleep problems. Without proper signals from the body's internal clock, a person may have difficulty falling asleep while waking up at night or be unable to sleep as long as they would like until morning. Total sleep may be reduced, and disrupted circadian rhythms can also mean shallower, fragmented, and lower quality sleep.
In addition, studies have identified circadian rhythm disruptions as a possible cause of obstructive sleep apnea (OSA), a sleep disorder characterized by repeated pauses in breathing. OSA reduces the body's oxygen levels and causes numerous sleep interruptions during the night.
Given the important role of sleep in productivity and overall health, a disrupted circadian rhythm often has significant consequences. Overall, an improperly adjusted circadian rhythm can negatively affect sleep in many ways and increase the risk of insomnia and excessive daytime sleepiness.
