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Chronotherapy: Being in Synch with the Internal Clock

Even though we are continuously changing by evolution, we are still very much connected to our original form as human beings and to the natural forces. Almost all of our body functions are controlled by a 24-hour cycle in which light plays a major role. Chronotherapy uses this fascinating knowledge of the biological clock of the human being.
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Chronotherapy has evolved from Chronobiology and both fields use the knowledge about the important 'clocks' in nature and their effects - including those on the human body. Researchers already know of many negative consequences that may result if the daily rhythm is turned upside down. Chronotherapy looks for the best possible treatments that adjusts to the patient’s internal clock, for example by determining the most suitable time for the patient to receive a treatment or medication in order to improve its efficacy and tolerance.

Chronobiology deals with the rhythmic course of biological mechanisms. We can detect a rhythmic pattern in many vital functions of the human being: take for example the rhythm of the heartbeat or pulse, the sleep-wake rhythm and also the approximate monthly rhythm of the menstrual cycle of a woman. The so-called circadian rhythm is particularly important. 'Circadian' (from lat. circa dies) means that the duration of the period corresponds more or less to the length of a day. Other rhythms that are in harmony with the natural environment are for example the circatidal rhythms (approximately six hours) or the circalunar rhythms (about 28 days).

It is interesting to note that the body sticks to the circadian rhythm - especially when it comes to the sleep-wake rhythm and to the body temperature - even if it does not receive any adequate signal from outside. This leads to the assumption that the circadian rhythm is part of the body itself. This has been proven in studies in which the subjects were left in a soundproof room with no windows for several days and still were able to maintain their rhythm.

It is also known that blind people are able to maintain their circadian rhythm if they still have their photosensitive retinal ganglion cells intact. These photoreceptors were discovered recently. Until then it was thought that only the rods and cones in the eye were able to process the light pulses. Now we know that they work in conjunction with the photosensitive ganglion cells in order to respond to light pulses and that they are connected to the control center for the circadian clock in the brain. The abbreviation for these ganglion cells is ipRGC (intrinsic photosensitive Retinal Ganglion Cells). These photosensitive receptors are connected with the SCN (suprachiasmatic nucleus) - the 'master clock' of the body - and with other regions of the brain that specially react to the light of the blue range. If these ipRGC are no longer intact or suffer deterioration - as it may be the case with glaucoma patients - the result is also a shift in the rhythm sleep-wake phases of the patients, as well as producing daytime fatigue and lowering performance.

There are internal and external factors that set up the rhythm. On the one hand, there is the body's own internal clock. On the other hand we have the environmental factors among which light is an important 'timer'. However, the intensity of the light has to be higher than 2000-2500 lux in order to cause any effect on the body.

There is more than one internal clock

All these interactions in the body are more complex than it seems at a first glance. If you think that with this basic information you have already learned enough about this subject, your body will prove you wrong. In fact, you also have to consider the reactions that take place when light reaches the skin. Certain types of nerve cells in the skin are also able to forward light pulses. For example, the body needs to receive the UV-B rays from the sunlight through the skin in order to be able to produce vitamin D.

It is also important to realize that there are multiple internal clocks. The 'master clock', located in the SCN, is the superior body clock. It coordinates the time-related procedures with all the other internal clocks located in the organs and cells. The SCN could be described as a nod of nerve cells in the brain, only a few centimeters behind the nose. When there is a successful coordination of the master clock with all the other internal clocks the body increases its chances to be in good health. After all, many procedures such as the absorption of nutrients, the digestion, the energy production and the detoxification of the body depend a lot on these rhythms.

Several decades ago it was discovered that when taking certain drugs, the time of the day when it was done played an important role and made a difference. Based on this knowledge, possible side effects could be reduced. Chronotherapy uses another important knowledge and tool: light therapy. It proved to be particularly successful when treating SAD patients. There are well known consequences of lack of light in the dark winter months, also known as 'winter blues' or 'Seasonal Affective Disorder' (SAD). Some of the symptoms of winter depression include mood swings, increased appetite, concentration problems and lethargy. It is possible to reduce these symptoms effectively by staying more time outdoors during the day or with a regular use of light therapy lamps that achieve a light intensity of up to 10,000 Lux in order to compensate the lack of natural light during the shorter days of the year. However, the duration of the exposure also plays an important role. If the eyes are exposed to the bright light for about 20-30 minutes a day, a first therapeutic success can already be noticed after 4-5 days.

Nowadays, light therapy is also used successfully for treating insomnia, since light is a significant 'timer'. In such cases, it is best to use light with intensity higher than 2500 lux, and with a particular white color that is very similar to daylight. Chronotherapy also tried to achieve improvements of the daily rhythm on cancer patients, as well as on elderly people in retirement homes, where light therapy lamps and light showers helped to slow down the reversal of the sleep-wake rhythm.

The color of the light also affects the body

There are some areas of chronobiology that need further investigation in order to learn more about the interaction between the time of the day and the functions of the organs in order to apply targeted chronotherapy. We know for example that drinking alcohol in the morning is much more harmful to the body than drinking it later during the day or towards the evening. However, the research on the precise daily rhythm of the liver, which plays such an important role when it comes to the detoxification of the body, has not yet been completed. It would for example provide helpful insights for improvements in the field of medication.

A relatively well known and also proven aspect of light therapy is its usage for treating delayed sleep-phase disorder (DSPD) or advanced sleep-phase syndrome (ASPS). There has also been progress in research with regards to the effect of the light spectrum. Light has a different effect on the body, depending on the color of the light. There are certain receptors in our brain that react more to the blue spectrum of the light, and others more to the red one. In general, it could be observed that even the small amounts of blue light that televisions, computer screens or displays of smartphones and tablets emit can cause sleep problems if these devices are used during the hours before going to bed. In fact, the shortwave blue light revives the body. Red light, however, is a longwave light. Together with the yellow colors of the light spectrum, it is able to calm and relax the body.

Therefore, we can observe that a certain amount of light pollution at night can upset the body rhythm. Sleep disorders are a clear sign that something is wrong with the internal clock of the body. People with sleeping problems are therefore recommended not to sit in front of the computer or television screen during the hours before going to bed, so that the high blue content of the light would not affect the internal clock.
If these external light pulses reach certain intensity they may in fact be much stronger than the body's biological clock. We see it happen when it comes to jet lag or shift work. In such cases, all what the body's internal clock can do is to adapt to the external factors. In case of night shifts, it may even have to completely reverse the sleep-wake rhythm.

Even though we have our own sleep-wake rhythm, which is our own internal clock, our body reacts to external influences and depends on them, especially on the sunlight. We cannot live without them for long periods of time and not suffer harm.

The sleep-wake cycle is part of the biorhythm, as well as the increased activities of certain organs of the body at certain times of the day. It would be very enlightening to know one’s own biorhythm and to better understand the signals of the body!

What happens if we ignore our inner body clock?

Even though the pace of the biological clock is slightly different in each person, there are some similarities. As stated, the biological clock is located in the SCN in the brain. This sort of node contains about 20,000 neurons, controlling the circadian rhythm that has an approximate length of 24 hours. The surrounding light or also the absence of light is an important factor. For example, darkness is necessary for the production of the sleep hormone melatonin, while the influence of daylight starts certain other processes in the body.

Light is often perceived as a self-evident source and people hardly distinguish, whether they are surrounded by sunlight or a bright artificial light. The quality and intensity of the light, however, is very important in order to estimate its effect on the body.

If we paid attention to how much time we really spend outside in natural light, we would perhaps be surprised at the small amount compared to being indoors with artificial light. The need to spend time indoors due to education, work, travel, errands, and also diseases, often comes up to many hours a day. Compared to natural sunlight on a summer day, the average illumination of the rooms indoors often corresponds to only one thousandth of the natural light.

In addition, shift work, flights over several time zones and the seasons, influence the amount of light that should reach our body. After all, our hormones, neurotransmitters, inflammatory factors and growth factors, as well as many other mechanisms, depend on the sunlight.

Proper use of external factors

When it comes to light therapy with the use of artificial light, we should not forget that there are different sources of artificial light. The light intensity of a conventional home lighting (between 50 and 100 lux) is very different from a powerful light therapy lamp that is designed for exactly this purpose, and provides at least 2500 lux or at best 10000 lux in a comfortable distance. Just for comparison: the light intensity on a summer day outdoors is approximately 50000-100000 lux. Light therapy lamps differ by factors such as intensity, color spectrum and the duration of the treatment or the distance from the eyes. Therefore, you can select one according to your individual needs.

Light therapy has the big advantage that it is based on the natural effect of light and using its opportunities. There is no need of drugs with side effects. Instead, light therapy offers a method by which the light information reaches the body through the eye - same as with natural light - or through the ear canal, where it gets to the light-sensitive receptors in the brain.

In addition to the traditional light therapy lamps that you can put on a table or mount on the wall, there is also an innovative light therapy device from Finland. This small device created by the Valkee Company uses the light information not through the eyes but through the ear canal. It features two plugs with small LEDs to insert them like headphones into the ears. The light intensity of each earplug is 10000 lux, and the emitted light is a full spectrum light, corresponding more than 90% to sunlight. The Valkee offers you innumerable ways to use the light therapy in everyday life: at home while preparing and eating breakfast, when you are on the way to work or even when you are working in front of the computer.

The findings of chronobiology open possibilities for improving the lighting in interiors thanks to the knowledge of the biological processes in the body. Certain light therapy lamps with dimmers can also be used as living room lights, serving two purposes at the same time.

We will certainly see some more developments in the field of chronobiology. The fascinating interrelations of nature are far from being completely explored. For chronotherapy, however, the road is clear for using the present findings and implementing them successfully. There are various possibilities for cooperation with the pharmaceutical industry, manufacturers of light therapy devices and architects. The more we know about the internal processes in the body, the better we can use external factors for the benefit of the human being. Chronotherapy is no longer limited to the proper timing of medication and the treatment of certain diseases. It already deals with preventive measures as well in order to avoid the development of diseases beforehand. This can be done with preventive light therapy to avoid SAD symptoms by improving the interior lighting or with architectural changes that take the rhythms of the body into consideration.
Published on 17.09. by Thomas Toernell
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