We’re constantly being told we’re not getting enough sleep.
And that a lack of shuteye could have knock on effects on our physical and mental health.
But new research has revealed that clocking up too many ZZZs could also have some negative impacts.
Researchers at Western University analysed the sleep habits of more than 10,000 participants – the largest project of its kind in the world – and found that getting too much sleep could be as bad for your brain as getting too little.
Participants were selected from an existing pool of more than 40,000 who signed on to be part of the world’s largest multi-national sleep study, launched in June 2017.
The study by Western’s Brain and Mind Institute and published in the journal SLEEP, confirmed sleep experts long-held belief that seven to eight hours of sleep each night is the holy grail in terms of brain performance.
For the research participants were asked to complete an online profile which included giving details about their sleep, medical history, mental health history, age and education level.
They were also asked to complete an online cognitive assessment shortly after waking up from a night’s snooze.
The games and puzzles tested a range of abilities including verbal reasoning, inhibition, short-term memory, spatial working memory and selective attention.
Researchers found the people who slept four hours or less gave a worse performance in their cognitive tasks than participants who had slept well.
But the same proved true for people who over-slept.
What’s more that particular pattern held true for people of all ages in the study.
The study found that the two traits that were most impacted by sleep duration were reasoning and language skills, while short-term memory was relatively unaffected by the amount of hours spent sleeping.
“Cognition declines as we get older, and, for those people sleeping four hours or less, it was as if we had aged them almost 10 years,” lead study author Dr Conor Wild, a neuroscientist at University of Western Ontario, told Daily Mail Online.
“And it goes equally for those who sleep too much,’ he added.
Why does too much sleep have a similar impact on brain function as too little sleep?
Experts say that spending too long in bed can cause something called ‘sleep inertia.’
When we wake up normally, during non-REM (Rapid Eye Movement) sleep, our heart rates are slower, our brain is less active and our blood pressure is lower.
This means that waking up can be less of shock to the system.
But when you wake up in the middle of REM sleep, ie after a prolonged sleep, that gets interrupted causing us to feel groggy.
“When you sleep too much on a regular basis you have a harder time coming out of the fog and cognition is slightly impaired as a result,” Dr Wild explained.
The sleep study follows research released earlier this year revealing that getting too much sleep could be bad for our health.
A study by researchers from Seoul National University, and published in the journal BMC Public Health, found that women who sleep for ten hours were 40 per cent more likely to have at least three health conditions linked to premature mortality.
These include a large waist, high blood pressure, elevated levels of fat or sugar in the blood.
Men didn’t escape the too much/too little sleep trap either as the research also revealed men who habitually slept fewer than six hours every 24 hours were also associated with an elevated waist circumference.
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