Seven hours may be the ideal amount of time for people in middle and old age to sleep, new research suggests.
In a study from the University of Cambridge and China’s Fudan University, nearly 500,000 British adults between the ages of 38 and 73 completed surveys about their sleep. Many also completed cognitive tests, and about a third completed a survey on their mental health and well-being.
The results showed that participants who said they slept an average of about seven hours a day did best in the cognitive tests, had the lowest symptoms of anxiety and depression, and had the highest feelings of well-being.
Even those who slept more than seven hours did not do as well as those who slept seven. “For every hour that you moved away from seven hours you got worse,” study co-author Barbara Sahakian told The Guardian.
Brain scans done on almost 40,000 participants showed that the areas of the brain most affected by sleep included the memory center.
However, Sahakian said the researchers are not yet sure why too much sleep could have a negative effect, although one idea was that people might spend longer in bed if they sleep poorly and wake up a lot.
However, Russell Foster, a sleep expert at the University of Oxford who did not take part in the study, disagreed with the results, telling CNN that the ideal amount of sleep is different for everyone, and that “one size does not fit all.”
Sahakian said that getting a good night’s sleep is important for people of all ages, adding, “I think it is as important as getting exercise.”