Insufficient Sleep May Influence Cognition in Teens With Overweight and Obesity

Adolescents with higher levels of adiposity appeared to be more susceptible to the negative cognitive effects of sleep restriction compared with those with lower levels of adiposity, a randomized crossover trial showed.

In a sample of 61 participants who were randomized to restricted or adequate sleep, those with a body mass index (BMI) in the 85th percentile or higher had lower cognitive scores after restricted sleep, reported Aaron Fobian, PhD, of the University of Alabama at Birmingham, and co-authors:

• Global cognition: mean restricted score 98.0; mean adequate score 103.2
• Fluid cognition: mean restricted score 94.5; mean adequate score 102.0
• Cognitive flexibility: mean restricted score 84.8; mean adequate score 92.8

No differences in cognitive scores emerged between the two sleep groups among adolescents with a BMI in the 5th to below the 85th percentile, they noted in JAMA Neurology.

Adolescents with overweight or obesity also had poorer attention scores following restricted sleep compared with their healthy-weight counterparts (mean 80.0 vs 88.4). There were no differences between the groups after adequate sleep.

Findings were similar when using total body fat percentage instead of BMI.

“Contrary to some of the literature, we didn’t find differences between individuals with overweight and obesity or with normal weight on cognition,” Fobian told MedPage Today. “Some studies have found that. However, we only found differences in response to when they’re sleep deprived.”

Co-author Lindsay Stager, MA, also of the University of Alabama at Birmingham, pointed out that even one night of less sleep had “significantly different impacts for people with overweight and obesity. For a lot of teenagers, school start times make it really hard to get the appropriate amount of sleep, and so if we’re thinking about it from an equity perspective … who is going to be the most vulnerable from the social and environmental limitations on sleep?”

Previous research has implicated sleep in the association between adiposity and cognitive function, the authors noted. Poor sleep is also associated with increased adiposity, increased appetite, and poorer nutritional food choices through increased levels of hormones like ghrelin, leptin, and cortisol.

However, “the causal mechanisms underlying [the association between obesity and cognitive difficulties] are unclear, perhaps due to its complex and multifaceted nature,” they wrote.

“For example, neuroanatomical differences may relate to impairments in cognitive function that subsequently predict increased food consumption,” they added. “Alternatively, biological factors related to obesity, including low-grade inflammation and insulin resistance, may exacerbate or independently predict cognitive impairments.”

For this study, participants ages 14-19 were recruited via Facebook and flyers in community locations, and eligibility was assessed over the phone. They were excluded if they had a sleep disorder, eating disorder, use of medications impacting sleep or appetite, learning disorders or disabilities, feeding or eating difficulties, BMI under the 5th percentile, or scores above 4.5 of 5 on the food fussiness subscale of the Childhood Eating Behaviors Questionnaire (CEBQ).

The study was conducted from September 2020 to October 2022, and 61 adolescents were enrolled (mean age 16.3, 57.4% female). Caregivers completed the Demographics and Food Questionnaire and CEBQ, and adolescents completed bioelectrical impedance analysis, height and weight measurements, and a cognitive battery, consisting of the National Institutes of Health Cognitive Toolbox, reflecting global and fluid cognition, and subscales evaluating cognitive flexibility, working memory, episodic memory, attention, and processing speed; and Stroop Task inhibition scores.

Participants were randomized to two sleep conditions: 9 hours of sleep (adequate) and 4 hours of sleep (restricted). Both had a washout period of two adequate nights of sleep beforehand. A lab visit was scheduled for after each sleep condition, between 6:00 a.m. and 2:30 p.m., and if actigraphy using wrist-worn actigraphs showed that participants met the sleep parameters, they completed the cognitive battery (and rescheduled otherwise).

Notably, the study used total body fat percentage in addition to BMI, which does not differentiate between adipose tissue and muscle mass and is considered an imperfect measure.

When using total body fat percentage instead of BMI, statistically significant sleep-related differences in fluid cognition, cognitive flexibility, and processing speed were observed only in 14.75% of the total study sample — adolescents in the highest total body fat percentage ranges. However, cutoffs for pediatric overweight and obesity when using total body fat percentages are often much lower than these ranges.

“The cutoffs for total body fat percent were much higher, and it really wasn’t the whole group with overweight and obesity [who had sleep-related differences in cognitive function], but more that extreme end,” said Stager. “And so … in research, when we group individuals by BMI classification, we might be incorrectly classifying some people as having greater risk.”

Stager also noted that “weight stigma is so important in this research and how we communicate this research.”

The researchers did not have a sample large enough to look at the relationship between weight stigma and sleep, but “when we’re talking about weight with patients, it’s broader than just eating and physical activity, and sleep is a really important piece to consider when a patient is coming to you with weight concerns or health concerns related to overweight and obesity,” she said.

Study limitations included variable at-home sleep conditions, and the re-administration of cognitive batteries, which could result in learning and improved performance. In addition, participants who completed the study had greater global cognition scores than those who did not. “Participation in the study involved simultaneous management of multiple factors, including sleep schedules and appointment times and dates, and may have presented an unappealing cognitive burden for some participants,” Fobian and team wrote.

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