Circadian rhythms: definition and examples.

The results of numerous studies have established a link between circadian rhythm disorders and certain diseases such as Alzheimer's or bipolarity.

Definition of circadian rhythms

Circadian rhythms are the set of biochemical, behavioral and physiological cycles that occur in our body over a 24-hour period.

Variations in body temperature, blood circulation, urine production, hormone production, food rhythms or even the rhythm of cognitive functions are regulated by well-defined cycles.

But the most important thing is that this internal clock regulates the state of activity and the state of sleep. Certain cells in the retina capture sunlight and allow us to be in tune with the earth's cycle: sleeping at night and being awake during the day. Disorders appear when your internal clock no longer matches the cycle of the sun.

Your organism therefore responds to a perfect logic in its rhythms which, if they are altered, can have physical consequences. and psychological.

What is the connection between our circadian rhythms and our sleep?

Our bodies are programmed to live during the day and sleep at night. The light-dark cycle links our environment to our biological clock. Our internal rhythm is therefore regulated mainly by this factor. Other elements may come into consideration, such as work schedules or leisure activities.
It is not uncommon to observe sleep disturbances related to disruption of circadian rhythms.

Phase delay and phase advance syndromes:

Le phase delay is a sleep disorder which results in late falling asleep and therefore delayed waking.

As this is incompatible with daily life, people with this syndrome will still have to get up early to meet their daily obligations. This will generate a lack of sleep which can result in difficulty concentrating, relationship difficulties and attention disorders which can lead to road accidents.
This disorder is one of the most frequently observed.

Conversely, phase advance characterizes people who go to bed abnormally early. Having trouble staying up between 6 p.m. and 9 p.m., sufferers will wake up very early in the morning and feel great.

Although few people are victims of it, it remains difficult, if not impossible, to live in permanent lag.

Night work

You should know that working hours at night or at different times (at the factory, for example) can alter your sleep cycle.

Being out of step with the Earth's rhythm, your biological clock is somehow "out of sync". Its symptoms are substantially the same as in the case of a phase delay.

They can affect the quality of your work and put your safety at risk. When you go on vacation, jet lag can also cause circadian rhythm disorders. There are solutions to deal with these different scenarios.

Circadian rhythm disturbances related to bipolarity?

Many studies have been conducted and published in the journal Biological Psychiatry to establish a link between the alteration of these rhythms and the onset of bipolar disorder.

 somatostatin is a neurotransmitter that helps moderate levels of anxiety and depression. It has been proven that, if this hormone was not present in sufficient quantity at the level of the amygdala gland, it could favor the appearance of bipolar disorders.

This absence of somatostatin is thought to be due to a dysfunction of circadian rhythms.

Excess anxiety occurring in bipolar people could come from poor regulation of somatostatin during sleep.

The circadian rhythms of hormones

Many physiological elements are subject to endogenous variations on a daily basis. These cycles have an impact on the production of hormones in our body. Melatonin, the sleep hormone, is hardly present in our body during the day. On the other hand, the closer we get to night, the more it is secreted. It is at its highest during the night, between 2 am and 3 am.

cortisol, known primarily for the regulation of metabolism, is present in high quantities upon waking. It stimulates the body and helps it get going. The growth hormone, somatotropin, is produced at the beginning of the night, during the deep slow-wave sleep phase. In children, it is essential for the development of muscles and bones. It acts on adult metabolism by helping to burn fat and contributing to protein synthesis.

Endogenous circadian rhythms are therefore of paramount importance to our physical and psychological health.

Correlation between circadian rhythm disorders and Alzheimer's disease.

People with Alzheimer's disease very often have a circadian rhythm failure, and more specifically an alteration of the alternation of sleep/wake phases. The greater the cognitive disorders of the patient, the greater the disturbances of this rhythm will be.

The most common symptoms are numerous nocturnal awakenings, which can go as far as sleepwalking, and feeling sleepy during the day. A recently published study demonstrated that these circadian imbalances lead to the progression of amyloid plaques in the brain. These are directly linked to Alzheimer's disease.

Normally, amyloid levels drop during sleep. Older studies have shown that these levels rise when the circadian rhythm is disrupted.

The presence of amyloid plaques in the brain is one of the triggers of Alzheimer's disease.