Everyone's body has its own rhythm. Some people do fine with little sleep, while others are groggy in the morning if they have had any less than seven hours. Some night owls just start feeling tired at 2 a.m.; other people have to be in bed by 11 p.m. But as different as our sleeping habits are, we all follow the cycle of our biological clocks.
Even though it varies from person to person, our sleep-wake cycle is largely controlled by our biological clock. The natural day-night rhythm and the alternation between light and dark tells special receptors in our eyes when our bodies must produce which hormones. At nightfall, our body begins to release the hormone melatonin which makes us sleepy; in the morning it releases the stimulant serotonin.
But these biological reactions have been seriously disturbed since the age of electric light. The sun used to steer people's lives and everyday routines, but we have become independent of natural sources of light. We can use electric light to turn night into day but we also spend a lot of time in enclosed indoor spaces. Although it is always light indoors, the light is much less intense than outside. Outdoor light intensity ranges from between 8,000 lux on a cloudy day to 100,000 lux on a sunny summer's day – compared to a mere 500 lux at home.
But electric light is not the only factor to disrupt our body clock rhythm. Cross-country and international journeys to different time zones, shift work, or the especially bright light of our smartphones all throw our natural system off balance. The result is that we feel tired when we should be wide awake, and awake when it is way past time to go to bed.
All this makes the time we spend in bed so precious. Bed is the place where we should be balancing out our body clock for a few hours. The best way to do it is to turn off all the lights in the bedroom and let our bodies enjoy complete darkness. A wake-up light which imitates sunrise is recommendable to make waking up in the morning better. Another fact: the more comfortable and supportive your bed, the better your body can use the dark and quiet to regenerate itself.