• Even small differences in sleep impact adolescents’ cognitive abilities

Teenagers who go to bed earlier and sleep for longer than their peers tend to have sharper mental skills and score better on cognitive tests, researchers have said.

A study of more than 3,000 adolescents showed that those who turned in the earliest, slept the longest, and had the lowest sleeping heart rates outperformed the others on reading, vocabulary, problem solving and other mental tests. The researchers expected teenagers with healthy sleeping habits to score better than those who slept poorly, but were surprised at the impact of even small differences in sleep mode. “We think that it’s the sleep that is driving the better cognitive abilities, in part because we consolidate our memories during sleep,” said a Professor of Clinical Neuropsychology at the University of Cambridge, England, Barbara Sahakian.

Sahakian’s team and researchers at the Fudan University in Shanghai, China, analysed data from 3,222 young people in the adolescent brain cognitive development study, the largest long-term investigation into brain development and child health in the United States. Those who took part had brain scans, cognitive tests, and tracked their sleep using Fitbits.

Even those with the best sleeping habits got less sleep than the experts recommend, the study found.

According to the American Academy of Sleep Medicine, 13- to 18-year-olds should have eight to 10 hours of sleep per night. The teenagers fell into three distinct groups. The first, about 39%, went to bed the latest and woke the earliest, sleeping on average seven hours and 10 minutes a night. The second group, about 24%, slept for seven hours and 21 minutes on average. The third, about 37%, went to bed the earliest, slept the longest, and had the lowest sleeping heart rates. They slept about seven hours and 25 minutes.

While there were no meaningful differences in the educational achievements of the different groups, those in group three scored the highest on cognitive tests, followed by group two, while group one scored the worst. Brain scans showed that those in group three had the largest brain volumes and best brain functions. Details are published in Cell Reports.

Sahakian said that it was “surprising” that minor differences in sleep had such an impact, adding: “It suggests that small differences in sleep amounts accrue over time to make a big difference in outcomes.”

For teenagers who want to improve their sleep and boost mental skills, Sahakian recommends regular exercise to help with sleep, and not using mobile phones or computers late in the evening.

(The Guardian)