We’ve all heard that adults need at least eight hours of sleep a night to function at our best, but recent research says that might not be the case. A study of more than 500-thousand people suggests that may be too much snoozing for those between 38 and 72 years old who are interested in improved memory, focus and problem-solving.
The study finds the sweet spot for sleep may actually be seven hours. That’s the ideal amount of snoozing for cognitive performance and for mental health, as researchers found symptoms for anxiety and depression were worse for people who were sleeping for longer or shorter amounts of time. Those who slept too much or too little were more likely to do worse on tests measuring mental processing speed and to show worse memory and problem-solving skills than the seven hour sleepers.
But it’s not just how long you sleep, consistency is important as well. So you can’t just sleep four hours one night and 10 the next for an average of seven hours and get the same benefits. It has to be seven hours habitually to see the results. “For every hour that you moved away from seven hours, you got worse,” explains study co-author Dr. Barbara Sahakian, noting that they’re still not really sure why too much sleep has a negative effect, “We don’t really understand why sleeping longer would be a problem.”