Preliminary results from the world's largest sleep study have shown that people who, on average, sleep between 7 and 8 hours a night performed more cognitively than those who slept less or more than this. 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 survey, which includes an in-depth questionnaire and series of cognitive performance activities.
“We really wanted to capture the sleep habits of people around the world. Obviously, there have been many smaller sleep studies of people in labs, but we wanted to know what sleep in the real world looks like," said the researcher. “People who logged in gave us a lot of information about themselves, we had a pretty extensive questionnaire and they told us things like what drugs they were taking, how old they were, where they were in the world and what kind of education they had ,” as these are all factors that contributed to some of the results.”
About half of all participants typically reported less than 6.3 hours per night, about an hour less than the study's recommended amount. A surprising 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 behavior was the same for everyone (7 to 8 hours), regardless of age. Also, the disorder associated with too little or too much sleep did not depend on the age of the participants.
“We've found that the optimal amount of sleep for your brain to perform at its best is 7 to 8 hours a night and that's in line with what the doctors will say you need to keep your body in top shape, too. That people who slept more than that were just as bad as those who slept too little," says the study's lead author.
The 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 from the findings of most scientific studies of complete sleep deprivation and suggests that not getting enough sleep for an extended period of time affects your brain differently than staying up all night.
On the plus side, there was some evidence that even sleep at night can affect a person's ability to think. Participants who slept more than usual the night before participating in the study outperformed those who slept their usual amount or less.
