Among the findings of the world’s largest sleep study—involving more than 40,000 people around the world—was the conclusion that too much or too little sleep can significantly affect your thinking skills. In the study, published in the journal SLEEP, volunteers participated in an online investigation that explored time spent sleeping and other health factors and tested them on a variety of cognitive activities. Not surprisingly, researchers found that sleeping seven to eight hours a night was associated with the best cognitive performance. That amount of sleep time has been recommended by health experts for many years.
In the study, though, researchers found that about half of the participants sleep, on average, less than 6.3 hours per night. The researchers found that the brain functions most affected by sleep were reasoning and verbal abilities. Tests of these functions found that sleeping less than seven or eight hours or sleeping more than that amount can impair those brain skills. The study also found that people who sleep less than four hours a night performed as if they were nine years older. One encouraging finding was that getting just one good night’s sleep can improve your cognitive ability the next day. Researchers emphasized, however, that getting seven or eight hours of sleep every night is a critical factor for better, long-term brain health.