Sleep was not considered very important until we realised the direct correlation between lack of rest and various health problems, such as heart disease, obesity and anxiety. Until the mid-1990’s, our pace of life was simpler: work ended when we left the office, shops were closed on a Sunday and the idea of being constantly connected did not even occur to us. Then, very quickly, even the idea of eight hours’ sleep became an extravagant legend!
In the UK, people sleep an average of six and a half hours a night, but the majority sleeps only six hours and 7% of people admit to only sleeping three hours a night. Artificial light, technology, and travelling by aeroplane, are all enemies of the natural process that we call sleep. We are extremely adaptable creatures, but we cannot maintain this pace for too long.
The circadian rhythm is a 24 hour cycle managed by our body clock. This clock works from the depths of our brain, to regulate sleep patterns and eating habits, hormone production, the regulation of our body temperature, our mood and digestion, in a process that lasts 24 hours, and is the product of millions of years of evolution, which works in perfect harmony with the earth’s rotation. For example, our bodies produce melatonin between 9 at night and 6 in the morning, at 3:30 am our body temperature is at its lowest of the whole day, the moment when we are most vigilant is around 10 in the morning, and our cardiovascular efficiency reaches its peak at 5 in the afternoon.
Sleep is regulated by another component, the homeostatic pressure of sleep, which is the indicator of our need to rest. This intuitive need is activated from the moment we wake up, and the longer we are awake, the greater it becomes. In healthy mice, during waking hours, about eighty proteins accumulate chemical markers at regular intervals, which add up the time elapsed since they last slept. The more markers there are, the more the need for sleep becomes urgent. Sleeping resets the system, returning the proteins to their initial condition, and wiping away the markers.
When we sleep regularly, our homeostatic pressure, which is our need for sleep, will reach its peak in coincidence with our circadian impulse, allowing us to hit the ideal window for sleep. During the night, we tend to reach our ideal time-frame for effective sleep around 2 or 3 in the morning.