The Reason Behind Why We Lose Sleep As We Grow Older Revealed; Believed To Be An Evolutionary Survival Trait
- The reason why we tend to lose sleep as we grow older may have finally been revealed.
- In this session, we will learn about the reason behind the increase in restlessness and sleeplessness at night with increasing age.
The Backdrop
With age, good sleep at night becomes even more elusive. But, what elderly people often label as insomnia may actually have been one of the evolutionary survival traits that helped in keeping their ancestors alive.
A new study of the modern hunter-gatherers from Africa hints at the same thing. Researchers found that when family members of different ages live together, the discrepancy in their sleeping patterns guarantees that at least one person in the group is awake or sleeping very lightly, at any given moment.
The research also suggests that incompatible sleep schema and restless nights may be an evolutionary leftover from a time thousands of years ago when a predator could be on the prowl at night time.
“A lot of older people go to doctors complaining that they wake up early and can’t get back to sleep,”
said author Charlie Nunn, a professor of evolutionary anthropology at Duke University.
“But maybe there’s nothing wrong with them. Maybe some of the medical issues we have today could be explained not as disorders, but as a relic of an evolutionary past in which they were beneficial.
Anytime you have a mixed-age group population, some go to bed early, some later. If you’re older you’re more of a morning lark. If you’re younger you’re more of a night owl. If you’re in a lighter stage of sleep you’d be more attuned to any kind of threat in the environment.”
The Experiment
The theory, which the researchers dubbed as ‘poorly sleeping grandparent hypothesis,’ was assessed on the Hadza people.
These northern Tanzania people still subsist by hunting and gathering. They live and sleep in groups, with 20 to 30 people in each one.
During the daytime, men and women branch out to look for food near Lake Eyasi. Reuniting together at night, they sleep outside, next to their hearth, or in grass huts.
“They are as modern as you and me, but they do tell an important part of the human evolutionary story because they live a lifestyle that is the most similar to our hunting and gathering past,”
Alyssa Crittenden, the co-author and an associate professor of anthropology at the University of Nevada said,
“They sleep on the ground, and have no synthetic lighting or controlled climate traits that characterized the ancestral sleeping environment for early humans.”
Study
Thirty-three healthy men and women, ages 20 to 60, participated in the study. They were to wear a small watch-like device on their wrists for 20 days, so as to record their nocturnal movement.
Result
The study result showed that the Hadza sleep patterns were rarely in harmony. While some hit the sack as early as 8 pm and woke up at 6 am, others dozed until after 8 am, not turning in until 11 pm. In between that, many roused from siesta several times during the night, for various purposes.
The study team found that out of more than 220 total observation hours, there were only 18 minutes when all adults were sound asleep concurrently.
On average, more than 1/3 of the group was attentive or nodding very lightly, at any given time. Researchers also found that the asymmetrical sleep schedules were age-related; people in their 50s and 60s generally slept and woke up earlier than those in their 20s and 30s.
Previous Study Results
There have already been previous researches which have found similar patterns in organisms like birds, mice, etc. The recent study is the first to test the occurrence in humans.
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Explanation
The study team believes that for much of our human history, living and sleeping in mixed-age groups with different sleep habits helped our ancestors to keep an observant eye on their surroundings and make it through the night.
They found that because of that very evolutionary trait, the Hadza people do not need to post any sentries to keep an eye on.
“The idea that there’s a benefit to living with grandparents has been around for a while, but this study extends that idea to vigilance during night time sleep,”
said Dr. David Samson, the study author from Duke University, North Carolina.
Article Courtesy: The Telegraph
