Sleep Problems in Schoolchildren Linked to Lower Fitness, Wellbeing and Grades

A sweeping study of nearly a thousand schoolchildren on Spain’s Canary Islands has found that children who report more sleep problems also tend to be less active, less fit, heavier around the middle, less satisfied with their health, and less successful in the classroom. The research, published in the Journal of Activity, Sedentary and Sleep Behaviors, is among the first to examine this wide constellation of outcomes simultaneously in a single school-based sample, offering an unusually integrated snapshot of how troubled sleep travels through nearly every domain of a child’s daily functioning.

The investigation was led by Daniel Arriscado-Alsina of the Universidad de La Laguna and Raúl Jiménez-Boraita of the Universidad Internacional de La Rioja. Their team recruited 949 students aged 9 to 15 years from 60 schools across the islands of Tenerife and Gran Canaria. The breadth of the sampling frame matters: by drawing participants from dozens of schools rather than a handful of classrooms, the researchers reduced the risk that their findings reflect the quirks of one particular educational environment. The study protocol was approved by the Research Ethics and Animal Welfare Committee of the University of La Laguna, and written informed consent was obtained from the parents or legal guardians of every participating student.

Sleep problems were measured with the Sleep Self-Report questionnaire, a validated instrument completed by the children themselves rather than their parents. This design choice is technically significant. Self-reported sleep captures the child’s own experience of difficulties such as trouble falling asleep, waking during the night, or feeling unrefreshed in the morning, which may diverge from parental observation. Each participant’s score placed them somewhere along a continuum of sleep difficulties, and the researchers divided the sample into tertiles, or three groups of roughly equal size ranging from the fewest to the most reported problems, to test whether outcomes shifted systematically across those groups.

The measurement battery extended far beyond sleep. Moderate-to-vigorous physical activity and sedentary time were assessed through questionnaires, as were health-related quality of life and the children’s own perception of their academic performance. Body composition was evaluated using anthropometric techniques, including the body mass index-for-age z-score, a standard pediatric metric that expresses a child’s BMI relative to population norms for their age and sex, and waist circumference, a direct marker of central adiposity. Physical fitness was tested in the field using handgrip strength measured with a dynamometer, the standing long jump as an index of lower-body explosive power, and a cardiorespiratory fitness test. Academic functioning was captured both through official grades and through the students’ self-assessment of how well they were doing at school.

Because students clustered within schools, the analysts used statistical methods that account for such grouping, examining differences across the sleep-problem tertiles with cluster-adjusted analyses. They then built separate generalized estimating equation models for each indicator, a technique well suited to repeated or correlated observations within groups. Each model was adjusted for sex, age treated as a continuous variable, family affluence, and area of residence, with school included as the clustering variable. The handgrip strength model received an additional layer of statistical control for body weight and height, since stronger children tend to be larger, and raw grip strength can therefore confound comparisons across body sizes.

The pattern of results was strikingly coherent. Higher sleep-problem scores were inversely associated with moderate-to-vigorous physical activity, health-related quality of life, standing long jump performance, cardiorespiratory fitness, academic grades, and perceived academic performance. In other words, as reported sleep difficulties rose, every one of these indicators fell. The inverse associations extended across domains that are usually studied in isolation: a child’s nighttime struggles showed up in the gymnasium, in the classroom, and in their own sense of wellbeing. Conversely, sleep problems were positively associated with sedentary time, the BMI-for-age z-score, and waist circumference, meaning children with more sleep difficulties tended to sit more and carry more central body fat.

One result broke from the pattern. Handgrip strength, a measure of isometric upper-body strength, showed no significant association with sleep problems once the model was adjusted for body weight and height. This null finding is informative rather than disappointing. It suggests that the apparent relationship between sleep difficulties and grip strength may be largely explained by differences in body size, whereas the associations with explosive lower-body power and cardiovascular endurance appear to persist independently of the adjustments applied. The distinction hints that different components of physical fitness may relate to sleep through different physiological pathways, a question the authors flag for future work.

The researchers also applied a false-discovery-rate correction, a statistical safeguard used when many associations are tested at once. Because a large battery of indicators multiplies the chances that at least some associations will appear significant by chance alone, this correction recalibrates the threshold for significance across the entire set of tests. The fact that all significant associations survived this stricter procedure strengthens confidence that the reported links are not statistical artifacts, even though the study’s cross-sectional design still limits the strength of the conclusions that can be drawn.

Indeed, the authors are explicit about the limits of their evidence. Because the data were collected at a single point in time, the indicator-specific models do not establish independence, temporal ordering, or causality. The relationships could run in either direction, or both. A child who sleeps poorly may feel too fatigued to exercise, and reduced physical activity is itself known to disrupt sleep, creating a potential feedback loop. Similarly, poor sleep can impair attention and memory, dragging down grades, while academic stress and screen-heavy evenings can in turn delay bedtime. Rising adiposity and poor sleep are also thought to reinforce one another through metabolic and hormonal pathways, including alterations in appetite regulation and circadian rhythm. Disentangling these reciprocal dynamics requires longitudinal designs that follow the same children over months and years, and the study’s authors call for exactly that.

Even with those caveats, the findings carry practical weight for schools, families, and public health planners. Sleep problems in childhood and early adolescence are common, modifiable, and increasingly recognized as relevant to school health, yet lifestyle, fitness, wellbeing, body composition, and academic functioning are not always assessed together in school-based research. By measuring all of these domains in one coordinated effort, the Canary Islands study demonstrates that sleep sits at the intersection of nearly every indicator educators and clinicians care about. If future longitudinal work confirms that sleep difficulties drive downstream harm, or that improving sleep lifts activity, fitness, and learning, then sleep could become one of the most efficient levers available for improving children’s health on multiple fronts at once. For now, the message is a sobering correlation: the children struggling most with sleep are, on average, the same children struggling most with movement, weight, wellbeing, and school.

Subject of Research: Associations between sleep problems and lifestyle, body composition, fitness, wellbeing, and academic outcomes in schoolchildren

Article Title: Associations of sleep problems with lifestyle, health-related quality of life, body composition, physical fitness, and academic performance in schoolchildren

Article References: Arriscado-Alsina, D., & Jiménez-Boraita, R. (2026). Associations of sleep problems with lifestyle, health-related quality of life, body composition, physical fitness, and academic performance in schoolchildren. Journal of Activity, Sedentary and Sleep Behaviors. https://doi.org/10.1186/s44167-026-00116-z

Image Credits: AI Generated

DOI: 10.1186/s44167-026-00116-z

Keywords: sleep problems, schoolchildren, physical activity, sedentary behavior, physical fitness, health-related quality of life, body composition, obesity, academic performance, cardiorespiratory fitness, cross-sectional study, adolescent health