Can you really catch up on lost sleep?
You snooze, you lose – researchers advance competing theories on a great mystery, writes Robert Matthews
Feeling groggy this morning? Welcome to the club. About 90 per cent of UAE residents reportedly get less than eight hours sleep a night. And the effect is more than just drifting off at your desk.
Studies have shown that insufficient sleep can lead to ill-health and an early grave. But now there may be a remedy, which is making up for lost sleep at the weekend.
A study of the sleeping habits of more than 38,000 Swedish adults found the detrimental effects of getting barely five of hours of sleep during the week were cancelled out by getting at least nine hours a night during the weekend.
The findings, reported in the
Journal of Sleep Research, have caused controversy among sleep researchers who have long argued it is impossible to catch up on lost sleep.
While one may feel temporarily revived by a decent lie-in, earlier research suggested that the cumulative effect of inadequate sleep cannot be undone. Studies on animals have found that the effects may include permanent brain damage.
The authors of the new research admit their findings are open to other interpretations and need corroboration. That seems wise in the light of what is known about sleeping, which most of us spend about a third of our lives doing. Why do we sleep?
The most obvious explanation is to conserve energy. But studies have found that a whole night’s sleep cuts our energy use by just 150 calories – barely 5 to 10 per cent of our total daily energy expenditure, which is equal to a 30 gram bar of chocolate.
Yet at the same time, sleep must be doing something important. Every living thing from fruitflies to blue whales devotes a chunk of their life to it in one form or another, despite the fact that the act of sleep leaves them vulnerable to predators.
One widely held theory is that sleep is vital for healthy brain function. Research suggests that the reduced sensory input gives the brain time to do some cleaning out and repair for the next day’s hard thinking.
But last year, researchers in the US showed that even a type of jellyfish with no brain at all seems to slumber at night, becoming far less responsive to stimuli such as food. Whatever its purpose, it is becoming clear that too much sleep is at least as bad as too little.
Insufficient sleep has long been associated with health effects ranging from obesity and diabetes to heart attacks to strokes.
Last year, a comprehensive review of the evidence from more than 150 studies published in the journal Sleep Medicine showed that less than six hours of sleep a night increased the risk of early death by about 12 per cent compared to those getting an hour or so more.
Now the same team of Japanese researchers has carried out a similarly comprehensive review of the impact of too much sleep. Published this month in
Sleep Medicine Reviews, the findings show the risk of early death increases by almost 40 per cent among those spending more than nine hours asleep each night.
Why this is remains unknown. It is not even clear if the link between time asleep and health effects is genuine or not. It is possible that sleeping either a lot or very little is just a symptom of the real cause of the strokes and heart attacks.
What is not in doubt is that not getting enough sleep seriously undermines mental performance. Studies show that key functions such as memory, vigilance and decision-making plummet when we are deprived of the sleep we need.
But how much is that? As ever, there is little consensus. Some researchers say the often quoted figure of eight hours lacks solid scientific support.
If there is a consensus, it is reflected in guidance given by the National Sleep Foundation in the US. Issued in 2015, this stressed the need for different amounts of sleep at different times of our lives.
The foundation said that while pre-schoolers aged 3 to 5 should be getting about 10 to 13 hours, youths between 14 and 17 need eight to 10 hours, while adults need seven to nine hours.
But the foundation concedes that some people can cope perfectly well on as few as six hours of sleep a night and as many as 10.
All this raises questions about headline-grabbing polls suggesting that virtually all of us are staggering around like zombies.
There was the statistic that 90 per cent of UAE residents are sleep deprived, which emerged from a survey by the health insurance firm Bupa Global and was based on the assumption that everyone needs at least eight hours a night.
In common with many other such surveys, its findings were also based on self-reported responses. While far simpler and cheaper than monitoring people, this can lead to unreliable conclusions as nutritionists have found after checking the food diaries of obese people.
This has led some researchers to question the widely accepted notion that there is a global crisis of sleep deprivation caused by our screen-gazing lives.
A 2012 survey of international trends in sleep duration by researchers at the University of Sydney found no consistent pattern between the 1960s and 2000s.
The truth is that sleep research is still in its infancy and it is high time the scientific community woke up to this.
Sleep research is a new science and so far, all that seems to have been agreed on is that there is no agreement