Here's why we lose sleep as we grow older

Recent study suggests why this may be a normal pattern

With increasing age, a good night's sleep becomes more difficult to achieve. But what people label as insomnia in reality may actually be an evolutionary survival trait that helped keep predecessors alive.



A study of modern hunter-gatherers in Africa found that when family members of all different ages live together, the differences in their sleeping patterns ensures that at least one person is awake, or sleeping very lightly, at all times, The Telegraph reported.

The research further suggested that mismatched sleep schedules and restless nights may be an evolutionary leftover from a time thousands of years ago when a lion might be on the prowl at 2:00am.

Author Charlie Nunn, professor of evolutionary anthropology said, "A lot of older people go to doctors complaining that they wake up early and can't get back to sleep."

"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. Any time 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," he added.

As part of a recent study, 33 healthy men and women aged 20 to 60 agreed to wear a small watch-like device on their wrists for 20 days to record their nighttime movements. The results showed that Hadza sleep patterns were rarely in synch with some members retiring as early as 8:00pm and waking at 6:00am while others snoozed until after 8:00am not going to bed until 11:00pm.

In between, many woke up from sleep several times during the night, getting up to smoke, tend to a crying baby or relieve themselves before nodding off again.

The researchers found that of more than 220 total hours of observation there were only 18 minutes when all adults were sound asleep simultaneously. On average, more than a third of the group was alert or dozing very lightly.

Previous studies have found similar patterns in birds, mice and other animals, but the study is the first time the phenomenon has been tested in humans, the research concluded.