Too Much Sleep Bad For Brain, Study Says


Source: University of Western Ontario

Summary: 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.


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. According to the study, approximately half of all participants reported typically sleeping less than 6.3 hours per night, 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 participants. 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. The study findings were published in the journal Sleep.

Sleep deprivation

Credit: University of Western Ontario

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 brain 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.

Prof. Adrian Owen said, “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.”


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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