Adolescents who enjoy longer sleep durations and adhere to earlier bedtimes demonstrate improved brain function, performing better on cognitive assessments, according to new research conducted by teams in the UK and China.
However, despite the observed benefits of better sleep habits, a study of U.S. adolescents reveals that even those with healthier sleep routines still fall short of meeting the recommended sleep durations for their age group.
Sleep plays a vital role in the body’s ability to function effectively. During sleep, the brain clears toxins, consolidates neural connections, and strengthens cognitive abilities such as memory, learning, and problem-solving. Additionally, sleep is known to boost immune function and promote mental health.
Adolescence, however, marks a period when sleep patterns often shift. Teens tend to stay up later and get less sleep, disrupting their internal body clocks. This period of reduced sleep coincides with significant brain development, making sleep especially important during this time. The American Academy of Sleep Medicine recommends that adolescents between the ages of 12 and 18 receive between 8 to 10 hours of sleep per night.
Despite extensive research on sleep in adults, little is known about its impact on adolescents, a critical developmental phase. The question of how much sleep young people are getting, and the effect this has on their cognitive performance, remains largely unanswered.
Professor Barbara Sahakian, a lead researcher from the University of Cambridge’s Department of Psychiatry, emphasized the lack of comprehensive data on adolescent sleep, particularly in relation to cognitive development.
To address this gap, researchers from Fudan University in Shanghai and the University of Cambridge turned to objective data from the Adolescent Brain Cognitive Development (ABCD) Study, the largest long-term research initiative focused on brain development and child health in the U.S.
For the study, over 3,200 adolescents aged 11 and 12 were provided with FitBits to track their sleep patterns. These data were cross-referenced with brain scans and cognitive test results. The team expanded their analysis to include a second group of adolescents aged 13 and 14, totaling around 1,190 participants. The study’s findings were published in Cell Reports.
The researchers identified three distinct sleep groups among the participants:
Group One: Representing approximately 39% of the adolescents, these individuals averaged 7 hours and 10 minutes of sleep. They typically went to bed late, fell asleep last, and woke up early.
Group Two: Accounting for 24% of participants, they averaged 7 hours and 21 minutes of sleep, with moderate sleep patterns across all characteristics.
Group Three: Comprising 37% of participants, this group averaged 7 hours and 25 minutes of sleep. They consistently went to bed earlier, fell asleep first, and exhibited lower heart rates during sleep.
While academic performance did not show significant variation across the three groups, cognitive tests assessing vocabulary, reading, problem-solving, and focus revealed notable differences. Group Three outperformed Group Two, and Group Two, in turn, outperformed Group One. Group Three also exhibited the largest brain volume and the most efficient brain function, while Group One showed the smallest brain volume and the lowest cognitive performance.
Professor Sahakian remarked, “Even though the sleep differences between the groups were relatively small—just over a quarter of an hour—there were still observable differences in brain structure, activity, and cognitive performance. This underscores the importance of quality sleep during this critical stage of life.”
Dr. Qing Ma, the study’s lead author from Fudan University, added, “While our research cannot definitively establish that improved sleep leads directly to better brain function, a growing body of evidence supports this idea. Previous studies have highlighted the role of sleep in memory consolidation, a process vital for learning.”
The researchers also analyzed the participants’ heart rates, noting that Group Three displayed the lowest heart rates across various sleep states, while Group One exhibited the highest. Lower heart rates are often indicative of better health, while higher heart rates are typically associated with poor sleep quality, such as frequent awakenings and excessive daytime sleepiness.
The longitudinal nature of the ABCD Study allows researchers to track changes over time, offering further insight into the long-term effects of sleep patterns on adolescent development.
The findings from this study underscore the importance of fostering healthy sleep habits in adolescents, particularly in light of their developmental needs. As sleep continues to be a cornerstone of cognitive and physical health, understanding its role during adolescence is crucial for promoting optimal growth and brain function.
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