The way our inner clock ticks

31 October 2016 - The sun rises every single morning and sets every evening. Every year is built up of seasons. Therefore, every day, every month and every year are subject to a rhythm which is defined by the sun in relation to the earth. Our body also follows individual rhythms, among them the most incisive, the wake-sleep cycle. Body temperature, hormone distribution and the female cycle are prone to biological rhythms as well. While man had to stay alive by way of hunting and collecting food, it was essential to closely adjust the wake-sleep cycle according to night and day. Using a full day of sunlight was essential for hunting prey and it was important to seek shelter and rest in a cave as soon as the sun set.

The wake-sleep cycle is defined by many factors, such as for example, sunlight. Another important factor is our hormone system. The hormone melatonin counts as one of the most important factors for influencing our rhythm. Due to its sleep-inducing effects, it is mainly released at night. Sunlight and strong artificial light sources block the production of melatonin. Cortisol – our body’s own stress hormone – regulates this rhythm as well. The distribution of cortisol happens at various moments throughout the day, the blood concentration being the highest in the morning and sinking over the course of a day. The cortisol peak in the mornings helps us wake up and makes us ready for the day.

Thanks to technological advancements, we have become more independent of natural rhythms. Artificial lighting enables a detachment from sunlight. We can now adjust our schedules to our needs and have more freedom in shaping our rhythms. For a long period of time, scientists thought that daily fluctuations in our body were relative to social factors such as the chosen time of waking up and going to bed, eating, and motor-driven activities. Newer studies have shown that we are in possession of an inner clock, which independently influences periodical changes in our bodies. Our inner clock can also synchronise with external factors, though. One of the main factors in such an influence remains the change between light and dark.

For most people, the optimal time for sleeping lies between 10 or 11 pm and 6 or 7 am. Yet this does not apply to every person. Individual sleeping habits allow people to be classified as early or late types. The larks go to bed early and wake up early, the owls are active late into the night and wake up at a later hour. These personal properties are mainly influenced by genes, which is why it is very hard to switch from being a lark to being an owl.

The requirements that the working world and a modern lifestyle puts on us lead to many people not listening to their biological rhythm. In the long run, this can affect our health and augment our risk of falling ill to many diseases. Shift workers, for example, more often suffer from depression, dependencies, metabolic syndromes, cardiovascular diseases and even tumors. Artificial light sources and the increase in light pollution in big cities, which prevents night time from being fully dark, are also accountable as possible reasons for a disturbed wake-sleep cycle or even insomnia.

Whether we’re an owl or lark type, our bodies will have to adjust twice a year in countries with daylight saving time. Since 1980, clocks switch between summer and regular time twice a year to more efficiently make use of daylight. In Germany and most European countries, as well is in North America, the time jumps one hour ahead in March, leading to a later sunset. Justified by its effect on saving electricity, the use of such a time change is widely debated today. It does nonetheless lead to our summer nights being light up to a later hour, which means we can spend more time outside before the sun sets. In October and November – according to the individual countries – time is set back again to ‘normal’.

Some of us might not even notice the shift in time, while others suffer immensely under the changed rhythm. Tiredness, insomnia, lack of concentration and headaches can occur up to a few days after the change. Other people have to adapt much more often to a change in their wake-sleep rhythm, such as shift workers or people who travel into another time zone for vacation or work. A so called jet lag occurs for a few days after travelling to a new time zone, leading to a disturbed wake-sleep rhythm and an impaired physical capacity. In the USA, taking melatonin is a popular method for overcoming jet lag and insomnia, even though the short term effect is critically questioned in scientific circles. Our body can overcome rapid changes of the day-night-cycle in some way or another. However, it is best to pay more attention to your inner clock and to adjust your daily life accordingly because the wake-sleep cycle plays an important role in our health.

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The way our inner clock ticks

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