For middle-aged to olderpeople looking to get the best sleep possible, seven hours of consistent sleep may be the sweet spot, new research suggests.
The study, published April 28 in the scientific journal “Nature Aging,” involved 498,277 people between ages 38 and 73 from the UK Biobank, a large-scale database with genetic and health information of U.K. participants.
Participants answered questions about how long they slept, completed an online mental health questionnaire and did problem-solving and memory exercises. Brain imaging and genetic data was provided for some participants as well.
“We wanted to know what is the perfect time that you should be sleeping for most middle-aged to older-aged people,” said Barbara Sahakian, a professor in the psychiatry department at the University of Cambridge who worked on the study. “How does that relate to other measures, for instance, your brain structure and your cognition, and your mental health?”
As people sleep, their brains work to consolidate memories and process things learned during the day, particularly during what’s called deep sleep, she said. Deep sleep may also allow people to purge toxins from their brains – and reduce the harmful deposits of an abnormal protein, amyloid.
But too little or too much sleep can create chronic stress. It can also cause changes in the hippocampus, a part of the brain vital to learning and memory, Sahakian said.
Researchers found participants performed better after seven hours of consistent sleep, she said. Those who got less or more had poorer cognitive performance and smaller brain volume, area and thickness.
But the study has its limitations, including the fact that participants reported only sleep duration versus sleep timing, sleep efficiency and circadian rhythm. Participants also reported their own sleep, leaving room for bias. They also recorded sleep times by the hour, not minutes.