Today's Edition
(NEUROSCIENCE NEWS)
A large-scale study conducted by researchers from the US and China has found that adolescents who go to bed earlier and get slightly more sleep show better brain function and higher cognitive test performance than their peers.
Using wearable devices and brain imaging from over 4,000 participants, researchers discovered that even small differences in sleep duration and timing impacted brain volume and task performance.
Teens with the earliest bedtimes had the healthiest sleep patterns, the largest brain volumes, and performed best on memory, vocabulary, and focus tasks. Despite the benefits, no group consistently met the recommended 8–10 hours of sleep, highlighting a broader sleep deficit during this critical developmental stage.
Just 15 minutes more sleep made measurable differences in brain health and cognitive performance in the study group, the researchers found.
Sleep plays an important role in helping human bodies function. It is thought that sleep helps clear out toxins that have built up in the brain, and brain connections are consolidated and pruned, enhancing memory, learning, and problem-solving skills. Sleep has also been shown to boost immune systems and improve mental health.
During adolescence, sleep patterns change, coinciding 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.
Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge said, “Regularly getting a good night’s sleep is important in helping us function properly, but while we know a lot about sleep in adulthood and later life, we know surprisingly little about sleep in adolescence, even though this is a crucial time in our development.
“How long do young people sleep for, for example, and what impact does this have on their brain function and cognitive performance?” she added.
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 US.
As part of the ABCD Study, more than 3,200 adolescents aged 11-12 years old were 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 team found that the adolescents could be divided broadly into one of three groups:
Group One, accounting for around 39% of participants, slept an average (mean) of 7 hours 10 mins. They tended to go to bed and fall asleep the latest and wake up the earliest.
Group Two, accounting for 24% of participants, slept an average of 7 hours 21 mins. They had average levels across all sleep characteristics.
Group Three, accounting for 37% of participants, slept an average of 7 hours 25 mins. They tended to go to bed and fall asleep the earliest and had lower heart rates during sleep.
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.
Professor Sahakian said: “Even though the differences in the amount of sleep that each group got was relatively small, at just over a quarter-of-an-hour between the best and worst sleepers, we could still see differences in brain structure and activity and in how well they did at tasks.
“This drives home to us just how important it is to have a good night’s sleep at this important time in life," she said.
First author Dr Qing Ma from Fudan University said, “Although our study can’t answer conclusively whether young people have better brain function and perform better at tests because they sleep better, there are a number of studies that would support this idea. For example, research has shown the benefits of sleep on memory, especially on memory consolidation, which is important for learning.”
The researchers also assessed the participants’ heart rates, finding that the group that slept the longest had the lowest heart rates across the sleep states. Lower heart rates are usually a sign of better health, whereas higher rates often accompany poor sleep quality like restless sleep, frequent awakenings and excessive daytime sleepiness.
Because the ABCD Study is a longitudinal study – that is, one that follows its participants over time – the team was able to show that the differences in sleep patterns, brain structure and function, and cognitive performance, tended to be present two years before and two years after the snapshot that they looked at.
Senior author Dr Wei Cheng from Fudan University added, “Given the importance of sleep, we now need to look at why some children go to bed later and sleep less than others. Is it because of playing videogames or smartphones, for example, or is just that their body clocks do not tell them it’s time to sleep until later?”
