How to set your biological clock to your ideal daily routine?

The term "biological clock" is used in different contexts. But it always means that limited time is allotted to perform a certain function of the body. This also applies to the sleep-wake cycle. A person doesn’t just go to bed in the evening and wake up in the morning. Circadian rhythms are responsible for this. From this material you will learn what it is and whether it is possible to take control of this mechanism.

Circadian rhythm - what is it?

In 2021, American physiologists received the Nobel Prize for their contributions to the study of mechanisms called circadian rhythms. These are biological rhythms associated with the change of day and night. Scientists have found that there is a gene that controls daily changes in the body: • sleep and wakefulness; • hormone production; • speed of metabolic processes; • reactions to stress.

This gene encodes a protein that accumulates in cells at night. When the sun rises, the substance begins to be consumed. A person wakes up, and internal processes in his body accelerate. Simply put, the circadian rhythm is a mechanism that works based on the body's biological clock. It reflects the cyclical fluctuations that occur during the day.

circadian index increased

Found (19 posts)

cardiologist March 22, 2021 / Andrey3852… / St. Petersburg

Good afternoon. Please help me with some advice. A week ago, I began to experience unpleasant sensations in the heart area. I measured the pressure, it showed normal, but the icon was on... open

April 3, 2021 / Andrey3852…

Zholudev Alexander Arsenievich, I am 34 years old. Did an ultrasound of the heart. Here is the result: the LV is not enlarged. The myocardium is not thickened (IVS up to 10 mm, SV up to 9.5 mm). Local contractility disorders were not found. Global contractility is not impaired. False chord to the left IVS). LA is not ...

cardiologist October 3, 2021 / Tatyana / Novosibirsk

Popular articles Extensive myocardial infarction: causes, symptoms, diagnosis and treatment

… 67, min 57, max 95. Heart rate under load 142, min 108, max 175. Circadian index 174%. The circadian heart rate index is increased. During the day, the submaximal heart rate was reached (91% of the maximum possible for a given age). Singles … open

cardiologist December 22, 2021 / Olga / Kaluga

... sinus arrhythmia. Average heart rate 81; afternoon 91; at night 58. Maximum heart rate 147, minimum 48 at five in the morning. The circadian index is increased. HRV is preserved. Single single (1) stomach. extrasystole. Single single (25), double (36) above the stomach. ...open

cardiologist September 2, 2014 / Yaroslav / Irkutsk

...within normal values. The situational activity of the control system is adequate. The circadian index is increased. The structure of the cardiac complex with signs of SRGC. The electrical systole parameters are stable and the indicators are correct. Rhythm disturbances… open

cardiologist July 26, 2014 / @anonymous / Moscow

...increase in heart rate upon awakening. circadian index 1.56. circadian heart rate profile is increased. sinus rhythm with heart rate ... bradycardia with an average heart rate of 52 per minute. Moderate bradycardia during the day. circadian heart rate profile increased -1.56. single supraventricular extrasystole - total ... open

cardiologist May 17, 2013 / Elena / Ekaterinburg

..., min. 52, max. 103 Heart rate with average loads - 110, min. 82, max. — 164 Circadian index 160%. The circadian heart rate index is increased. During the day, submaximal heart rate is reached (95% of the maximum possible for a given age) Polymorphic ... open

cardiologist November 10, 2012 / Elena / 0

Question for the cardiologist. Dear doctor! I am writing to you with the following question:I am writing to you with the following question: Hello! help me understand what kind of illness I have. Hours... open

November 10, 2012 / Elena

... QRS. sinus rhythm with maximum heart rate -120 beats, MIN circadian index 1.15 - reduced. Elongation of QT-T MAX was recorded up to ... duration of prolonged QT-T = -15 min hypertensive index increased rate of morning SBP upon awakening, increased degree of decrease in nighttime BP ...

cardiologist September 8, 2012 / Anonymous

...can't get warm.

Daily ECG monitoring was prescribed, results:

“Severe bradycardia during the day. Circadian index 154%. The circadian heart rate index is increased.

During the day, submaximal heart rate was reached (76% ... open

cardiologist September 7, 2012 / Anonymous

...please, are there any serious disturbances in the functioning of the heart? Thank you!

Severe bradycardia during the day. Circadian index 154%. The circadian heart rate index is increased. During the day, submaximal heart rate was reached ( 76 ... open

cardiologist September 7, 2012 / Anonymous / 0

Question for the cardiologist. Dear doctor! I am writing to you with the following question: open

September 7, 2012 / Anonymous

... Holter studies Artem, 21 years old, 184/76 Thank you!

Severe bradycardia during the day. Circadian index 154%. The circadian heart rate index is increased. During the day, submaximal heart rate was reached (76% of ...

How does it work?

There is an external cycle of 24 hours: it is caused by the rotation of the Earth around the Sun. The biorhythm of every living creature adapts to it. In humans it is close to 24 hours (±15 minutes).

The body builds its ideal daily routine on its own, adapting to the cycle of day and night: • at 6:30 there is a sharp jump in blood pressure; • at 7:30 the production of melatonin (sleep hormone) stops; • at 8:30 intestinal motility is activated; • at 9:00 the concentration of testosterone reaches its maximum; • at 10:00 vigilance increases; • at 14:30 better coordination of movements is achieved; • at 15:30 a person has the fastest reactions; • at 17:00 the cardiovascular system works best; • at 18:30 the highest pressure is observed; • at 19:00 body temperature reaches its maximum; • at 21:00 melatonin begins to be produced; • at 22:30 intestinal motility is suppressed.

Thus, the body itself dictates when we need to wake up and go to bed, go to the toilet, exercise, and begin intellectual work. Keeping this routine in mind affects your health.

Results and discussion.

The results of the CI calculation are presented in Tables I and II. There is a high stability of CI in all groups of healthy subjects (Table I), regardless of gender, age and type of equipment used (CM, non-invasive/27/ or invasive blood pressure monitoring/10/). The CI value, based on our calculation based on the results of 20 studies combining the results of daily monitoring in 7870 healthy subjects aged 10 to 79 years (Table I), practically does not differ from the normative parameters we previously determined (1.32 + 0.06) /4-7/ and on average is 1.33 + 0.05. A study by J. Freitas et al. /17/ showed high reproducibility of the daily structure of heart rate, even when changing periods of sleep and wakefulness in shift workers.

We also compared the CI with the difference between the night and day values of the average RR interval in the indicated works (Table 1) and correlated these parameters with heart rate values. A significant correlation of the Night/day difference was noted with the night-time heart rate level (r = -0.61), while no significant interdependencies were identified between the heart rate and CI parameters. As can be seen from our calculations, the close dependence of this indicator on the initial heart rate level, high variability with age-related and physiological fluctuations in the average heart rate value (sinus bradycardia or tachycardia), even in healthy subjects, lead to the lack of stable normative standards in the assessment, which did not allow it has yet to find wide application in practice. The maximum Ndd value in our analyzed group of healthy people (N 19, Table 1) is almost 2 times (42%) higher than the minimum (N 2, Table 1), while CI in the same group does not differ significantly ( differences by 12%), NN 1 and 20 in Table 1.

We identified significant changes in the circadian profile of heart rhythm in patients with diseases of the cardiovascular system. Calculation of the CI index in the work of Molnar J. et al /21/ showed an increase in the rigidity of the circadian rhythm of the heart as the severity of the disease increased: CI 1.31, 1.24 and 1.1, respectively, in the control group of healthy people, in survivors and in patients who died suddenly with pathology of the cardiovascular system (dilated cardiomyopathies, heart attacks, idiopathic arrhythmias, arterial hypertension, etc.). In a study by G. Casolo et al. /12/, we noted a progressive smoothing of the circadian rhythm profile in patients with coronary heart disease and hypertrophic cardiomyopathy who died during observation, compared with survivors (CI 1.03 in dead and 1.09 in surviving patients ).

Determining the characteristics of the pathophysiological mechanisms underlying changes in circulatory system is possible by analyzing the circadian profile of the heart rhythm in groups of patients with verified disorders of the vegetative status. As an analysis of works studying the features of circadian rhythms in diabetic patients, a classic clinical model of autonomic imbalance, has shown, damage to both the parasympathetic and sympathetic parts of the nervous regulation of heart rhythm contributes to the formation of circadian rhythm rigidity. In all cases, the CI values we calculated were lower in patients with clinically pronounced total vegetopathy (NN 4,13,14,19. Table II), compared with diabetic patients without damage to the autonomic nervous system (NN 20, 24. Table. II). The importance of sympathetic denervation in the pathogenesis of decreased CI is confirmed by the analysis of the work of Hintze U. et al. /16/. When using the beta-blocker metropolol in patients over 70 years of age who have suffered a first myocardial infarction, there is an increase in the rigidity of the circadian rhythm (CI 1.16 at baseline and 1.13 after 6 months with constant use of metropolol), with the opposite dynamics of CI in the placebo group -control (1.13 at baseline and 1.2 after 6 months). The most demonstrative evidence of the influence of the autonomic nervous system on the formation of the circadian heart rate profile can be considered our analysis of the results of the classic study by D. Ewing et al. /15/. The authors assessed, based on the results of CM, heart rate variability in healthy people, in 3 groups of diabetic patients with varying degrees of severity of vegetopathy (without vegetopathy, with isolated parasympathetic denervation and total vegetopathy) and in patients with transplanted hearts, as a model of complete surgical denervation of the heart. Calculation of CI showed a progressive increase in the rigidity of the circadian heart rate profile as the degree of vegetopathy increases. The CI values were 1.41; 1.35; 1.25; 1.19 and 1.11, respectively, in the healthy control group, in diabetic patients without vegetopathy, with damage to parasympathetic innervation, total autonomic blockade and patients with transplanted hearts. Thus, the analysis allows us to assume that the basis for the persistent development of circadian rhythm rigidity (decrease in CI < 1.2) is the mechanism of total vegetopathy, with a violation of both the afferent and efferent links of the vagosympathetic regulation of heart rhythm, the development of the “denervated” phenomenon hearts. Smoothing of the circadian rhythm profile reflects the depletion of adaptive heart rhythm reserves and is clinically associated with a poor prognosis and a high risk of arrhythmogenic syncope and sudden death in patients at risk /12,15,19,21/. At the same time, in patients with severe neurological pathology, but without pronounced clinical signs of autonomic disorders (NN 22,23. Table II), the value of CI did not differ from the group of healthy people and patients with prognostically more favorable forms of arrhythmias (NN16,25,25 ,26,28.Table II).

The phenomenon of strengthening the circadian profile of the heart rhythm (increase in CI > 1.45) in our studies was noted in patients with idiopathic bidirectional ventricular tachycardia /7/. From the works of other authors, we noted an increase in CI in a study by Mathias C. et al./20/ in patients with chronic lesions of the nucleus tractus solitarius, a disease in which blockade of baroreceptor afferent impulses develops, but preservation of efferent symptomatic regulation, especially pronounced in response to physical , emotional stress /30/. Analysis of clinical work also confirms this assumption. Galassi A. et al./18/, assessing the circadian rhythm of the heart in patients with the so-called syndrome X (angina attacks in patients with normal coronary angiography), compared with patients with coronary heart disease and healthy volunteers, noted no differences in nighttime heart rate values in all groups, however, daily heart rate values were significantly higher in patients with syndrome X, which, when calculating CI, leads to an increase in this indicator. At the same time, the levels of adrenaline and norepinephrine in the blood plasma measured in this group of patients were not increased, which indicates the absence of a tonic increase in sympathetic activation and speaks more about increased sensitivity to catecholamines. In Pickering Th. et al./26/ CM was performed in 12 patients with extrasystole. Based on the values given in the work for daytime and nighttime heart rate levels for the group as a whole (75.5 + 9.5 and 61.2 + 12.7 beats/min, respectively), the calculation of the CI indicator was 1.26, i.e. did not go beyond the normative values we found. But when analyzing the individual dynamics of the heart rhythm in the examined patients, the maximum values of CI (1.68, 1.56 and 1.42) were noted in patients who were characterized by a decrease in the frequency of extrasystole at night by more than 90%. Only in patients with CI above 1.5, a pronounced increase in extrasystole was noted during bicycle ergometry.

In recent years, the calculation and interpretation of changes in CI based on the results of CM or 24-hour blood pressure monitoring have found widespread use in domestic clinical practice /35-45/. There are many studies in which we can talk about the demand for the use of CI, since the authors in a descriptive manner state a smoothing /46,47/ or strengthening of circadian rhythms of heart rate /48/, but without using a specific assessment parameter they cannot interpret the mechanism and clinical significance of these changes . This significantly complicates the clinical interpretation of the identified changes and does not provide the doctor with specific information to assess the patient’s condition and/or prognosis of the disease during treatment. The use of a standardized criterion for assessing the dynamics of the circadian rhythm of heart rate will help expand the diagnostic capabilities of CM, identify new pathogenetic links of cardiovascular diseases, and optimize the entire scheme of treatment and preventive measures in patients with cardiac pathology.

Conclusions:

1. The circadian index, calculated from the results of Holter or blood pressure monitoring as the ratio of the average heart rate during wakefulness to the average nighttime heart rate, reflects the basic structure of the circadian heart rate rhythm.
2. The CI value is within the range of 1.24 -1.44 USD. (M 1.32 + 0.06) is an indicator of the stable autonomic organization of the circadian rhythm of the heart.

2. A decrease in CI less than 1.2 is observed in diseases associated with autonomic “denervation” of the heart and is associated with a poor prognosis and a high risk of sudden death in patients at risk.

3. An increase in the circadian profile of the heart rate (increase in CI above 1.5) is associated with increased sensitivity of the heart rate to sympathetic stimulation.

For correspondence Dr.Med.Makarov L.M 127412 MNIIP and DH Ministry of Health of the Russian Federation, Moscow, Russia.

Tel. (095)483-2101. Email

The impact of circadian rhythms on health

Studying the human circadian rhythm has made it possible to understand the importance of waking up and going to bed on time. He explains why you shouldn't set your alarm earlier than 7:30, because your body needs time to prepare to come out of sleep. The daily biorhythm also causes harm to a nocturnal lifestyle and shift work, in which the endocrine and nervous systems literally get confused in the schedule.

Compliance with the cycle established by the internal clock allows you to : • normalize metabolic processes; • prevent digestive disorders; • take control of hormones; • achieve maximum efficiency at work; • enjoy physical activity.

Knowledge of biological rhythms tells you how to lead a healthy lifestyle and not experience stress from it. When the body receives what it needs on time, it is less susceptible to all kinds of diseases.

Symptoms of QI deviation

The circadian index is not a diagnosis or even a manifestation of a pathological process. We are talking about an instrumental result, a specially calculated indicator. Therefore, it is incorrect to talk about the clinical picture.

It is necessary to consider the pathological process that is behind this diagnostic finding, and there are many of them.

Standard symptoms that cause the circadian index to be below normal:

Heart rhythm disturbances

Usually a type of bradycardia of varying severity. From a slight drop in heart rate, which the patient does not even feel, to a critical level leading to Morgagni-Adams-Stokes attacks.

Usually we are talking about heart failure, a previous heart attack, cardiomyopathy and other abnormalities, including defects.

Dyspnea

Against a background of peace. After physical activity it increases several times. Lying down can result in asphyxia and death of the patient.

Typically, such a severe manifestation is observed in the decompensated phase of heart failure.

Chest pain syndrome

Slight or medium in strength. Appears after intense physical activity. Similar to that of angina pectoris.

The pain is pressing or burning, spreading in nature. They appear after activity and go away in a matter of minutes.

Cough

For no apparent reason. Pulmonary etiology cannot be excluded by eye. It is necessary to carry out at least an x-ray, only then there is a chance to delimit the pathological processes.

The symptom intensifies after physical activity and is not relieved by bronchodilators. Combined with shortness of breath and asphyxia. Continues almost constantly, does not leave the patient for a minute.

Extrasystole

Changing the intervals between each subsequent heartbeat. The essence of this condition is the appearance of extraordinary contractions at the moment of relaxation of cardiac structures (diastole).

Singles are not dangerous. But against the background of a decrease in the circadian index, group, paired extrasystoles (bigeminy) come to the fore. They pose a great threat to the patient's life. Urgent relief of the condition is necessary.

Dizziness

Develops as a result of a decrease in myocardial contractility. This phenomenon is indirectly confirmed by a decrease in the circadian index: a disruption in the normal nutrition of the brain affects it.

This is an unfavorable prognostic sign. The risk of stroke—an acute weakening of blood circulation in cerebral structures—is growing. Manifests itself as the impossibility of normal orientation in space. The world literally floats before your eyes, the earth disappears from under your feet.

Headache

Cephalgia. Localized in the area of the back of the head, crown. Baling in nature. Follows the beat of the heart. It intensifies after a change in body position and is accompanied by severe heaviness in the chest.

Nausea, vomiting

Reflexive in nature. Such manifestations are associated with a malnutrition of the brain, as in previous cases. Restoration of the normal state occurs independently.

Fainting

Syncope or disturbances of consciousness. They appear suddenly. As a rule, in the early stages they are short-term and appear rarely. The patient can be easily returned to normal. Then the process gets worse.

Rigidity of the circadian rhythm (instability, drop in level) affects a group of cardiac, respiratory and neurogenic manifestations.

How severe it is depends on the underlying disease. At the same time, it is possible to control the dynamics and course of the pathology, including using the specified value.

If the circadian index is elevated, there are most often no manifestations. This is not always good. There are several reasons: disruption of the nervous system, professional training, extrasystole and others.

The clinical picture in this case may be completely absent.

Circadian rhythm disorder

Sometimes desynchronization of a person’s internal rhythms and the external day-night cycle occurs. They are studied mainly by neurologists - in the context of disturbances in sleep and wakefulness.

Several types are considered: • Jet lag. Due to sudden movement between time zones (two or more), autonomic disorders (weakness, headache, disorientation, nausea) appear. • Sleep disturbance during shift work. Due to a failure in melatonin production, insomnia occurs, stress levels increase, and depression may develop. • Sleep phase disorder. Due to desynchronization, sleep comes late and, accordingly, awakening is delayed. Some people, on the contrary, fall asleep too early.

All this affects health. The body is forced to sharply adjust natural processes to the current regime. As a result, his life activity does not proceed as intended by nature.

Prevention of heart failure

Overweight people are at risk. In order for the heart to work stably and to avoid disturbances in the circadian index, it is necessary to lead an active lifestyle. It is enough to do 2 moderate-intensity workouts per week. Even people with cardiovascular diseases can perform aerobic exercise. The main thing is to monitor the state of the body during exercise. Excessive tension is indicated by chest pain, nausea, dizziness and shortness of breath, which makes it difficult to talk.

Health implications

Sleep must be timely. This time is dictated not by family, class schedules, work hours or personal preferences, but by biorhythms. The most obvious consequence of ignoring them is drowsiness during the day, up to the development of narcolepsy (short-term falling asleep while walking). This entails a decrease in concentration, which is fraught with deterioration in performance and the creation of emergency situations. If the daily routine is not followed, a person cannot fully rest.

Constant stay of the body in a state of fatigue in the long term is fraught with: • cardiovascular diseases; • hormonal imbalances; • metabolic disorders; • weakened immunity; • mental disorders; • oncological processes.

The risk of autoimmune diseases also increases. Working at night, when you need to sleep, the body enters into an internal confrontation with itself. And in any case, it will look for ways to stop this.

HOW TO IMPROVE THE WORK OF THE “MOTOR”

It is important to understand that normal heart function depends on many factors, from poor lifestyle to constant emotional stress.
In fact, our heart has a large margin of safety - it can work for up to 150 years. The following will help improve the functioning of the heart and maintain its health:

These high-frequency fluctuations are modified by a phenomenon called respiratory gating. It is assumed that low-frequency fluctuations in heart rate are based on Mayer waves of blood pressure, the main determinant of which is considered to be sympathetic vasomotor activity. Very low frequency fluctuations have been associated with the renin-angiotensin system, other humoral factors and thermoregulation.

Several types of different fractal scaling measures, force analyses, complexity measures, measures of symbolic dynamics, turbulence, and heart rate deceleration capacity have been studied in different patient populations. Loss of protective vagal activity is associated with a poor prognosis for various cardiovascular diseases and sudden cardiac death.

active lifestyle - just walk 5 km a day at an average pace and your heart will always be in good shape. It's only 1.0-1.5 hours of walking in the fresh air;
a good full night's sleep - ideally it should last 8 hours a day. A daytime nap of 0.5-1.5 hours will also not hurt;
calmness and stability - an established way of life, a constant schedule of work and rest is vital to our heart;
Regular visits to the doctor and undergoing preventive examinations - at least once a year, after 40 years - 2 times a year.

In addition, the heart needs certain vitamins and microelements, which must come from food. Heart-healthy foods include fresh fruits and vegetables, dairy-based and vegetarian soups.

We must always remember that the health and normal stable functioning of our heart depends primarily on ourselves. In order for the “motor” to work properly, it is necessary to create suitable conditions for it and take into account the characteristics of your body.

Assessment of circadian rhythms of cardiac activity during Holter monitoring. Taking into account the peculiarities of Holter monitoring (ECG recording under conditions of prolonged, practically unlimited activity), we can assume the existence of a number of criteria for assessing heart rhythm that are specific only to Holter monitoring and carry new significant clinical information. First of all, these are indicators of circadian ECG changes.

How to adjust your circadian rhythm?

Normal daily biorhythms are widely known. If it is discovered that the usual daily routine conflicts with them, the “clockwork” can be “repaired”. The “tool” will be daylight - the basis for the formation of a 24-hour cycle.

The main rule : the less light, the more melatonin. Therefore, in the morning you need to immediately open all the curtains, and if it’s dark outside, turn on the lamps. Closer to night, on the contrary, you should minimize the amount of light.

It turned out that photosensitive ganglion cells in the retina are responsible for the desire to sleep. They are the ones who record sunrise and sunset in order to transmit signals to the brain and start or stop the process of melatonin production. Therefore, our internal biorhythms depend on seeing light.

Circadian rhythms

Neuroscientist Russell Foster on the sleep-wake cycle, photosensitive retinal ganglion cells and circadian rhythm disorder

PostScience

The circadian rhythm is an endogenous biological rhythm with a period of about 24 hours. The simplest example is our sleep-wake cycle.

The circadian rhythm is needed to fine-tune all aspects of physiology and behavior to the demands of a 24-hour world. It anticipates daily changes in daylight hours, temperature, food availability, and even the behavior of predators and prepares the body in advance for changes in the environment so that it is fully adapted.

Clock cells

Circadian rhythms are common to almost all life forms, including single-celled life and bacteria. The body has a circadian clock at the molecular level that controls internal oscillations, the period of which is about 24 hours. This oscillation adjusts the internal physiological rhythm to the external 24-hour cycle. We know what makes the internal clock work: there are several important clock genes that produce clock proteins. They interact with each other, forming a molecular feedback loop that generates oscillations in clock proteins with a period close to 24 hours; the proteins then tell the cell when to do what and what time of day it is. We originally thought that circadian rhythms occurred when many different cells worked together to form a single network, but it is now believed that it is a property of individual cells.

In order for the circadian clock to benefit the body, it must be adjusted to the outside world. The most obvious example of a discrepancy between the internal clock and the outside world is jet lag: when we fly across multiple time zones, we need to adjust our internal clock to the local time, which is determined by the sunrise and sunset cycle. Photoreceptors record the duration of the light and dark phases of the cycle and send signals to the molecular clock mechanism to adjust the internal clock to the outside world. Humans are most sensitive to daily changes in the amount of light and darkness, but some animals, such as reptiles, also rely on daily changes in temperature to establish their biological rhythm. Adjustment to the outside world, no matter how it occurs, guarantees that at any hour all the cells of the body will perform the necessary processes at the right time of day.

Complex multicellular life forms often have a clock that coordinates all the others. In mammals, the control clock is located inside the brain and is called the suprachiasmatic nucleus. It receives information about light levels from the eyes and adjusts its 50,000 neurons accordingly, which then send out multiple signals to coordinate the rest of the body. To generate the circadian rhythm, clock cells in the suprachiasmatic nucleus use more than 14 different genes and their protein products.

Basic properties of circadian rhythms

Circadian rhythm is a special type of biological rhythm. Biological rhythm is a general term that describes any rhythmic process. Some rhythms are generated by the internal clock, while others are influenced by the environment. The biological rhythm generated by the clock will remain constant at constant light and temperature levels. In addition to the 24-hour circadian rhythms, there are clocks that run with a period of a year or 360 days, called circannual rhythms, which were discovered in organisms living on the seashore - their biological clocks have a period of about 12.8 hours.

We have known about 24-hour rhythms for a very long time: the ancient Greeks talked about daily changes in the body, but they thought that they were caused only by changes in the amount of light and temperature in the outside world. The first scientific experiment to identify circadian rhythms was carried out in 1729 by the French scientist and astronomer Jean-Jacques Dorthou de Meran: when he placed a plant in a dark place, he noticed that in constant darkness the leaves open and close with a rhythm close to 24 hours. This observation was the first fixed indication that biological rhythms could be set from within. After this, there were very few experiments, and this continued until the 1950s and 1960s, when the real properties of circadian rhythms were discovered.

The first property of the circadian rhythm is that under constant lighting conditions it remains unchanged. The rhythm period may be slightly longer or shorter than 24 hours in different species: the human clock is slightly longer, whereas the mouse clock is slightly shorter.

The second key property is that these rhythms are temperature compensated. This means that even if the outside temperature changes radically, the 24-hour rhythm does not speed up or slow down very much. This is extremely important, because if there were no temperature compensation, the circadian clock would not be able to accurately tell time.

The third key feature is that circadian rhythms are locked to an external 24-hour day. The main signal for adjusting the rhythm is light, although there are other signals, for example, temperature.

Some organisms can adjust their clocks based on the circadian behavior of other animals. For example, baby mice establish their circadian rhythms before and after birth based on their mother's hormonal signals: in the womb, the signals enter the blood through the placenta, and after birth through the milk. Later, when the axons between the eyes and the suprachiasmatic nucleus are already formed, the mice can rely on the level of light. Whether this happens in people the same way or not, we don’t know for sure. Another example: malaria parasites can tell the time of day by signals in the blood, and this encourages them to move at night to blood vessels very close to the skin, where mosquitoes pick up their blood. The mosquito then bites another person and infects another victim.

The importance of routine

The main advantage of having a clock is that it allows the body to anticipate predictable changes in the environment and proactively adjust physiology and behavior to changing conditions. For example, if you know that sunrise will be in three hours, you can begin to increase your metabolic rate, body temperature, muscle strength and blood flow and generally become active. All of this prepares you so that when morning comes, you will be active and able to take full advantage of your new environment. If we simply waited until morning to do this, we would spend a lot of time adjusting to the new environment, and during that time we would not be able to fully take advantage of the “new” conditions.

In the same way, at the end of the day, when we begin to fall asleep, the body's physiology begins to decline and shut down, preparing the brain and the rest of the body for sleep. During sleep, the brain is very busy: creating memories, processing information to find new solutions to complex problems, instructing the rest of the body to repair damaged tissue, repair metabolic pathways, and organize energy reserves. Some parts of the brain are more active when we sleep than when we're awake, so even though we're not moving, the brain is incredibly active, performing critical tasks for the next day. The ability to predict and anticipate, rather than simply react, gives an organism a huge selective advantage in the struggle for existence.

Some animals and plants also use circadian clocks to determine the season: if an organism measures daily changes in the amount of darkness and light, and if the duration of darkness increases or decreases, then it can determine the time of year very accurately. In the Northern Hemisphere, some mammals use the autumn increase in night length as a signal to prepare for hibernation, and in other animals, such as deer and sheep, it can prompt mating: autumn mating means that the young will develop over the winter and be born in the spring when the weather is usually good and there are many new plants to eat. There are mammals that change the thickness and color of their fur to prepare for winter: for example, Arctic foxes grow thicker, whiter fur in winter, which helps them camouflage and survive.

Humans also have seasonal biology. For most of us it's not very noticeable, but in general people often report changes in appetite and weight gain during the winter months, and some people become more depressed during this time. How these changes occur is still unclear. It is likely that in the past we were more dependent on the seasons than we are now. This may be partly due to the fact that we now live in houses and are thus protected from the outside world and that the Earth's seasonal rhythms are no longer so sharply defined.

How to set the clock

The big question is: how does the eye detect light, which it uses to adjust circadian rhythms? Our team recently discovered that the eye contains a special set of light-sensitive cells called photosensitive retinal ganglion cells (pRGCs). These cells are very different from the cones and rods that detect light and create images. They are formed from ganglion cells, the axons of which emerge from the eye, assemble into the optic nerve and travel to the brain. About 1–2% of these cells have a blue light-sensitive photopigment called OPN4. Photosensitive ganglion cells detect dawn and dusk and then set the molecular clock to the correct time of day.

Another key discovery was that blind people, as well as those whose cones and rods are damaged due to genetic diseases, can have completely normal and functional photosensitive ganglion cells. So these people are blind, but from the point of view of the clockwork they see. This has important implications for medical practice, and ophthalmologists should advise blind patients with intact photosensitive cells to receive enough light to properly regulate circadian rhythms. Ophthalmologists now understand that the eye is an organ that gives us both a sense of space (vision) and a sense of time (circadian regulation). This understanding changed the way we define blindness and how we treat eye diseases.

It is important to emphasize that if you have no eyes at all, then all adjustment based on light is lost. In the past, some people have claimed that we have photoreceptors in the brain and even behind the knee, but such claims have never been supported by scientific research. Without eyes, most of us will go to bed about 30 minutes later each day than the previous day, since our internal rhythm is approximately 24 and a half, rather than exactly 24 hours. There are tragic situations where people are born without eyes or lose them in an accident, and work is currently underway to provide a "pharmacological replacement" for light - pills that trick the molecular machinery into thinking it sees light, and As a result, the clock is adjusted to the desired time.

There is also another problem with light: we don't get enough of it at the right time. We spend most of our time indoors, where the light is not bright enough for us to adjust the clock by it. This is a particularly serious problem for older people, whether they live in their own home or in a nursing home. However, when the amount of light received is increased, internal circadian ri can be restored, resulting in improved brain function. Eating meals at the same time and even exercising in the morning have also been shown to help people maintain good sleep patterns.

Circadian rhythms and sleep

In developed and increasingly developing countries, where society lives 24/7, we urgently need to restore proper sleep patterns. Our 24-hour sleep rhythm is the most obvious circadian rhythm observed in humans and many animals, but sleep is more than just part of the circadian system. Sleep is a highly complex state created by multiple brain regions, neurotransmitter systems, and modulators. Because of this complexity, sleep is very vulnerable to disturbances. Recent work has shown that sleep and circadian rhythm disorders (SCRD) are common across a variety of neurodegenerative and neuropsychiatric diseases in which neurotransmitter pathways are disrupted. For example, SCRD occurs in more than 80% of patients with depression or schizophrenia. Feeling sleepy at the wrong time is certainly inconvenient, but this is just the tip of the iceberg. SCRD is also associated with a wide range of interrelated pathologies, such as poor attention and memory, decreased mental and physical reaction speed, decreased motivation, depression, insomnia, metabolic disorders, obesity, immune disorders and even an increased risk of cancer. All of them are often observed in both mental and neurodegenerative diseases.

Some indicators of the human circadian rhythm // wikimedia.org

We have made great strides in our understanding of the mechanisms that generate and regulate circadian rhythms and sleep, as well as in understanding the broader health issues associated with SCRD. All this provides us with a truly remarkable opportunity to work to ensure that society understands the full importance of sleep for human health. Sleep truly is our best medicine, and working at the wrong time can be disastrous—literally. Our attention levels reach their lowest point in the early morning: it is no coincidence that disasters such as Chernobyl and the Exxon Valdez tanker accident occurred during the night shift. Even taking into account fatigue and traffic volume, there are a disproportionate number of accidents at 4 am - more than at other times of the day.

Even if we cannot help everyone realize that they need to pay attention to sleep and prioritize it for its importance, understanding the mechanisms and pathways that generate and regulate sleep will allow us to develop new treatments and drugs that would are evidence-based and could improve the health and quality of life of many people with different diseases throughout society. The potential impact of helping people solve their sleep problems is huge, and we can do it. And what's really important to change is that currently most five-year medical training programs only cover sleep and circadian rhythms in one or two lectures.

This is a translation of an article from our English-language publication Serious Science. You can read the original version of the text by following the link.

About the author: Russell Foster – PhD, Head of the Nuffield Laboratory of Ophthalmology and the Sleep and Circadian Neuroscience Institute, Chair of Circadian Neuroscience, Nicholas Kurti Senior Fellow, Brasenose College, University of Oxford

Portal “Eternal Youth” 06/01/2017

How to deal with jet lag?

Studies have shown that movements to the west are easier to bear than to the east. The reason is that in the first case, sleep and awakening are postponed to a later time, and in the second - to an earlier time.

Long-haul flights do not occur often enough to cause significant pathologies. Therefore, the task of the traveler is to prevent the occurrence of symptoms that impair the quality of life.

To do this, it is recommended: • start gradually shifting the sleep-wake cycle a few days before the trip, so that the changes are not so drastic; • get as much sunlight as possible on the first morning in a new place; • before going to bed, ensure complete darkness (no gadgets, night lights).

If going to sleep proves too difficult, short-acting sleeping pills may be used. It is better to entrust the selection of the drug to a doctor.

How to normalize sleep when working shifts?

People who are forced to periodically work at night lose their circadian rhythms. Every day their daily routine changes, and the body barely has time to adjust from one cycle to another.

To normalize internal processes, neurologists recommend: • turning on the light during wakefulness; • provide complete darkness during sleep; • put on sunglasses several hours before you plan to fall asleep to gradually reduce melatonin production; • use earplugs and blackout masks while sleeping.

The social component of setting the biological clock is especially important. Household members must realize that the night worker’s health is at risk and not interfere with the creation of comfortable light conditions for him.

Who has sleep phase disorders?

To answer this question, it is necessary to separate people with true sleep phase disorders from those with certain chronotypes.

There are only three of them: • Morning (larks). The biological clock is shifted back by about three hours. • Asynchronous. The biological clock follows the normal circadian rhythm. • Evening (owls). The biological clock is moved forward by about three hours.

Owls and larks are not victims of bad habits. It’s just that in the former, the PER3 gene, which is responsible for circadian rhythms, is shortened, and in the latter, it is lengthened. People with an asynchronous chronotype are susceptible to phase shift syndrome. If their daily routine becomes desynchronized with the normal circadian rhythm, sleep disturbances and accompanying unpleasant symptoms begin. In larks such phenomena are rarely observed, in owls they are excluded in principle.

How to deal with sleep phase disorders?

A person with an asynchronous chronotype can eliminate this disorder by correcting the daily routine and light therapy. The specific actions depend on the desired direction of shift.

The problem is taking a long time to fall asleep, the solution is waking up earlier + light therapy during the day.
The problem is waking up earlier, the solution is light therapy in the evening.
The problem is a shift in sleep phases, the solution is a proportional delay in sleep and awakening until normalization.

If these measures do not help, it is possible to take exogenous melatonin, a synthetic hormone (endogenous is produced by the body itself). It allows you to adjust the time of the onset of biological night - the period of slowing down physiological processes and going to bed. Preparations based on this active substance (for example, Melaxen, Melarithm) are hypnotics; they regulate neuroendocrine functions. Therefore, they can only be taken under the supervision of a doctor.

What should larks and owls do?

The peculiarities of the circadian rhythms of people with morning and evening chronotypes are determined genetically, and not pathologically. There are not many pure larks and owls in nature - 15 and 20% of the total population of the planet.

Constructive solutions for them can be: • change of place of residence (owls are more comfortable in the west, larks - in the east); • optimization of sleep and rest patterns based on hours of maximum productivity (for larks - before 12:00, for owls - after 16:00); • distribution of types of activity in accordance with the characteristics of the chronotype (in the morning, hearing sensitivity is maximum from 7 to 13 o'clock, in the evening - from 19 to 1 o'clock).

There is no point in treating such people: they are not sick. Forcing them to follow a standard circadian rhythm is dangerous. This is tantamount to constantly forcibly knocking an ordinary person out of the standard biorhythm.

There is no need for sleeping pills here - they will only do harm. It is also better to abstain from excess coffee consumption: those with non-standard chronotypes are more prone to addiction.

ESSENCE OF THE METHOD

Holter cardiac monitoring is a special type of instrumental and electrophysiological diagnostics that allows you to record the main indicators of heart function throughout the day.

Items. We studied five healthy subjects with a mean age of 8 years. The study was approved by the appropriate institutional review boards. All participants provided written informed consent prior to participation.

Forced desynchronization protocol. To distinguish the influence on cardiac dynamics of the intrinsic circadian system while controlling for the diurnal pattern of behavior, we collected physiological data during a 10-day “forced desynchrony protocol” with subjects living in an individual suite. This protocol had two initial baseline acclimation periods with 8 hours of sleep and 16 hours of wakefulness.

The method was developed in 1961 by Norman Holter, an American biophysicist, after whom this type of research is named. Norman Holter did a tremendous job - he summarized many years of research experience carried out in the field of recording and studying electrical phenomena for more than 25 years.

During this study, a special portable heart rate recorder (HR) is used, which is attached to the patient’s body and produces a continuous recording of the electrocardiogram, stores it and transmits all the information to the computer.

Chemical analysis methods

Gaps in the signal indicate missing data. During each waking period, the same schedule is repeated so that statistically all behaviors are balanced across all circadian phases. Measurements. To provide a marker of endogenous circadian pacemaker, core body temperature was recorded during the 10-day protocol using a rectal temperature sensor with values stored on a computer once per minute. Analysis of fluctuation intensity. To assess correlations in heart rate fluctuations, we used fluctuation-attenuated analysis. For each 1-hour data segment, we estimated the scale exponent α over the same range of time scales, from 20 to 400 pulses.

Information about the heart rate recorded by a portable recorder is analyzed using a decoder - a computer equipped with specially developed programs for processing ECGs, which allow, based on algorithms for assessing the shape and duration of the complexes, to classify normal and pathological heart contractions. The analysis also includes the diagnosis of rhythm pauses without specifying their nature.

Scaling curves are vertically shifted for clarity. Significant circadian rhythms are observed when the α value for individual data deviates during both wake periods. Data are shown as symbols and cosinor model approaches are shown as lines. The results are consistent across all five subjects during the wake and sleep time periods. An individual sleep period is indicated when he lives outside the laboratory. Circadian rhythms group average scaling index α for wake periods and sleep periods.