The Evolutionary reason Why We Sleep Less as we Age

As people grow older, our resting time becomes shorter and we sleep less, but why?

Night is falling. As the streetlights turn on, the screens inside begin to illuminate. First the television: any series is good; suddenly, not so much. When it doesn't seem to be enough anymore, the deluge of pictures and videos on social media becomes a distraction for fifteen minutes, and half an hour later it becomes two. It's three o'clock in the morning, and sleep isn't coming. It's true: as we become older, we tend to need less sleep.

The older you get, the less sleep?

Sleep deprivation is not the only issue, as sleep hygiene deteriorates with age. So getting less sleep isn't just a matter of keeping your eyes closed for extended periods of time. It is rather related to the quality of sleep, which declines with age.

This condition should not be confused with the various chronotypes. These are the times of day when people are most productive, such as early morning, midnight, or early dawn. On the contrary, it appears that surveillance in the middle of the night, which deprives people of deep sleep, becomes more prevalent as they age.

Sleepiness, according to a study published in Proceedings of the Royal Society B, also has to do with the feeling of wakefulness we have during the night. Instead of falling into a deep, restful rest, older adults are prone to waking up at any time during the night. Not only that, but the constant presence of a screen with a seemingly endless supply of content to consume is definitely not helpful.

A bad period, eh?

The occurrence of this phenomenon in adolescents is very obvious. When they enter this stage of development, they tend to go to bed later and sleep less. And not only that. With constant exposure to visual stimuli - literally available in the palm of your hand - the brain is unable to settle into a zone of darkness where it can rest.

However, the phenomenon is not limited to those who constantly use social media and mobile devices at night. According to the Guardian, this habit is also observed in modern nomadic gatherer cultures in Tanzania. Adults' ability to sleep at night reduces as they get older because they have to keep an eye out for threats in the environment.

Taking care of others, the elders watch over the other members of the group. Known as the "grandmother hypothesis," this is one of the first lines of research suggesting that as humans age, not only does their ability to sleep decrease, but so does the quality of their sleep.

So it's possible that sleeping less isn't just a time-related sickness, but an evolutionary feature that allowed our species to survive when sleep was a matter of life and death. Back then, the youngest were given priority in terms of rest, while the elderly were taking care over them.