Too much sleep bad for brain, study says

October 9, 2018, University of Western Ontario
Too much sleep bad for brain, study says
Credit: University of Western Ontario

Preliminary results from the world's largest sleep study have shown that people who sleep on average between seven to eight hours per night performed better cognitively than those who slept less – or more – than this amount. Western neuroscientists at the Brain and Mind Institute released their findings today in Sleep.

According to the study, approximately half of all participants reported typically sleeping less than 6.3 hours per , about an hour less than the study's recommended amount. One startling revelation was that most participants who slept four hours or less performed as if they were almost nine years older.

Another surprising discovery was that sleep affected all adults equally. The amount of sleep associated with highly functional cognitive behaviour was the same for everyone (seven to eight hours), regardless of age. Also, the impairment associated with too little or too much sleep did not depend on the age of the .

"We found the optimum amount of sleep to keep your brain performing its best is seven to eight hours every night. That corresponds to what the doctors will tell you need to keep your body in tip-top shape, as well. We also found that people that slept more than that amount were equally impaired as those who slept too little," says Conor Wild, Owen Lab Research Associate and the study's lead author.

Participants' reasoning and verbal abilities were two of the actions most strongly affected by sleep while short-term memory performance was relatively unaffected. This is different than findings in most scientific studies of complete sleep deprivation and suggests that not getting enough sleep for an extended period affects your differently than staying up all night.

On the positive side, there was some evidence that even a single night's sleep can affect a person's ability to think. Participants who slept more than usual the night before participating in the study performed better than those who slept their usual amount or less.

The world's largest sleep study was launched in June 2017 and within days more than 40,000 people from around the world participated in the online scientific investigation, which includes an in-depth questionnaire and a series of cognitive performance activities.

"We really wanted to capture the sleeping habits of people around the entire globe. Obviously, there have been many smaller sleep studies of people in laboratories but we wanted to find out what sleep is like in the real world," said Adrian Owen, a Professor at The Brain and Mind Institute and the former Canada Excellence Research Chair in Cognitive Neuroscience and Imaging.

"People who logged in gave us a lot of information about themselves. We had a fairly extensive questionnaire and they told us things like which medications they were on, how old they were, where they were in the world and what kind of education they'd received because these are all factors that might have contributed to some of the results."

Explore further: Sleeping too much or too little may affect stroke risk differently based on race

More information: Conor J Wild et al. Dissociable effects of self-reported daily sleep duration on high-level cognitive abilities, Sleep (2018). DOI: 10.1093/sleep/zsy182

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5 / 5 (2) Oct 09, 2018
Were the sleep times forced? I doubt it. This would mean more sleep is not necessarily causative, and we certainly shouldn't assume that longer sleep is the cause, but a 'symptom' of what is causing brain problem. And/or it could be causative. Less sleep seems causative more so. But ultimately sleep times are not root causes anyway, factors are causing you to have less than ideal times. I mention this because such concepts as these seem to somehow often be conveyed 'as if we could just decide to change our habits'. But that is not how it works exactly.
5 / 5 (1) Oct 09, 2018
studies like this are usually so imperfect. people sleep more for SO many reasons.

one main reason people go through phases of sleeping more is recoving from infection. in addition to this, they can take antibiotics.

there are massive correlations between being sick and poor cognitifive performance. there are also correlations between taking anti-biotics, and immune reaction induced depression. as well as regularly old correlations between brain infections (menningitis of fever) and depression.

there are TOO MANY confounding factors that are causative to make these correlative studies about sleep particularly meaningful.

this is not horrible science, it's just below mediocre. it's the kind of science that hsouldn't be funded. it's noise.
not rated yet Oct 09, 2018
My sleep has been messed up since childhood. I go for months with 1 or 2 hours of sleep a day. I'll go 3-5 days with no sleep at all. Less frequently I'll sleep too much, 18 hours a day. Other times I'll go for a year or so with normal sleep. The results of this experiment are in line with my personal experience, not that that matters scientifically.

I have confounding factors. I have bipolar disorder which is associated with both too much and too little sleep. Medications that keep me awake or put me to sleep. For the most part though the reasons why don't matter--wrong amount of sleep=screwed up cognition. (Except during hypomania, then I feel clear headed on very little sleep.) I think the previous 2 comments overstate the problems w/ this experiment, not that my experience proves it, but 40k samples is pretty good especially coupled with the extensive questionnaires.

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