Summary: While the effects of sleep deprivation are well known, researchers discover sleeping too much could have a detrimental effect on your brain. A new study reports sleeping more than eight hours per night can reduce cognitive ability and reasoning skills.
Source: 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 Monday in the high-impact journal, SLEEP.
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.
“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 actions most strongly affected by sleep while short-term memory performance was relatively unaffected. This is different from 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 solid 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 included 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.”
Source: University of Western Ontario
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is adapted from the University of Western Ontario news release.
Video Source: Video credited to University of Western Ontario.
Original Research: Open access research for “Dissociable effects of self-reported daily sleep duration on high-level cognitive abilities” by Conor J Wild, Emily S Nichols, Michael E Battista, Bobby Stojanoski, and Adrian M Owen in Sleep. Published September 18 2018.
Dissociable effects of self-reported daily sleep duration on high-level cognitive abilities
Most people will at some point experience not getting enough sleep over a period of days, weeks, or months. However, the effects of this kind of everyday sleep restriction on high-level cognitive abilities—such as the ability to store and recall information in memory, solve problems, and communicate—remain poorly understood. In a global sample of over 10000 people, we demonstrated that cognitive performance, measured using a set of 12 well-established tests, is impaired in people who reported typically sleeping less, or more, than 7–8 hours per night—which was roughly half the sample. Crucially, performance was not impaired evenly across all cognitive domains. Typical sleep duration had no bearing on short-term memory performance, unlike reasoning and verbal skills, which were impaired by too little, or too much, sleep. In terms of overall cognition, a self-reported typical sleep duration of 4 hours per night was equivalent to aging 8 years. Also, sleeping more than usual the night before testing (closer to the optimal amount) was associated with better performance, suggesting that a single night’s sleep can benefit cognition. The relationship between sleep and cognition was invariant with respect to age, suggesting that the optimal amount of sleep is similar for all adult age groups, and that sleep-related impairments in cognition affect all ages equally. These findings have significant real-world implications, because many people, including those in positions of responsibility, operate on very little sleep and may suffer from impaired reasoning, problem-solving, and communications skills on a daily basis.