Physical Fitness and Sleep-Related Problems Among Adolescents: Findings From the EHDLA Study.

Physical fitness, particularly cardiorespiratory fitness, has been shown to positively impact sleep quality. However, the relationship between overall physical fitness and sleep-related problems in adolescents remains underexplored. Therefore, the aim of this study was to analyze the association between overall physical fitness and sleep-related problems in adolescents. This cross-sectional study included 812 adolescents (median age: 14 years [interquartile range = 12-17]; 54.9% girls) from the Eating Healthy and Daily Life Activities (EHDLA) data. Physical fitness was measured objectively using the Assessing the Levels of PHysical Activity and fitness (ALPHA-Fit) battery for children and adolescents and a flexibility test, while sleep-related problems were evaluated using the BEARS sleep screening tool (B = Bedtime problems, E = Excessive daytime sleepiness, A = Awakenings during the night, R = Regularity and duration of sleep, S = Snoring). Generalized linear models were used to examine the association of overall physical fitness with the different components of sleep-related problems. The odds of experiencing sleep-related problems decreased significantly with each kilogram increase in handgrip strength (odds ratio [OR] = 0.97, 95% confidence interval [CI] 0.94-0.99), and with each standard deviation increase in overall physical fitness (OR = 0.76, 95% CI 0.59-0.99). In contrast, despite not statistically significant, an increase in long jump appeared to reduce the sleep-related problems (OR = 0.91; 95% CI 0.82-1.02), while a longer time in the 4×10-m shuttle run test might increase sleep problems (OR = 1.12; 95% CI 0.98-1.28). In conclusion, greater levels of physical fitness, particularly muscular strength, may be key for reducing sleep-related problems, emphasizing the importance of personalized training programs.