Adolescents who sleep for longer – and from an earlier bedtime – than their peers tend to have improved brain function and perform better at cognitive tests, researchers from the UK and China have shown.
But the study of adolescents in the US also showed that even those with better sleeping habits were not reaching the amount of sleep recommended for their age group.
Sleep plays an important role in helping our bodies function. It is thought that while we are asleep, toxins that have built up in our brains are cleared out, and brain connections are consolidated and pruned, enhancing memory, learning, and problem-solving skills. Sleep has also been shown to boost our immune systems and improve our mental health.
During adolescence, our sleep patterns change. We tend to start going to bed later and sleeping less, which affects our body clocks. All of this coincides with a period of important development in our brain function and cognitive development. The American Academy of Sleep Medicine says that the ideal amount of sleep during this period is between eight- and 10-hours’ sleep.
Studies looking at how much sleep adolescents get usually rely on self-reporting, which can be inaccurate. To get around this, a team led by researchers at Fudan University, Shanghai, and the University of Cambridge turned to data from the Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term study of brain development and child health in the United States.
As part of the ABCD Study, more than 3,200 adolescents aged 11-12 years old had been given FitBits, allowing the researchers to look at objective data on their sleep patterns and to compare it against brain scans and results from cognitive tests. The team double-checked their results against two additional groups of 13-14 years old, totalling around 1,190 participants. The results are published today in Cell Reports.
The team found that the adolescents could be divided broadly into one of three groups:
Although the researchers found no significant differences in school achievement between the groups, when it came to cognitive tests looking at aspects such as vocabulary, reading, problem solving and focus, Group Three performed better than Group Two, which in turn performed better than Group One.
Group Three also had the largest brain volume and best brain functions, with Group One the smallest volume and poorest brain functions.