Dyssomnias Are Linked to Impaired Ventilatory Function in Young Athletes Regardless of Sex: A Cross-Sectional Study

Introduction: Sleep quality is recognized as a key determinant of sports performance, yet sleep disturbances are commonly observed among athletes, with a higher prevalence being reported in females. This study aimed to examine sex-specific associations of sleep disturbances with cardiorespiratory fitness, body composition, and metabolic flexibility in athletes. Methods: Fifty-nine athletes ( n = 22 females, 18–35 yr, 8%–45% body fat) underwent a 3-h assessment, including validated questionnaires for assessing insomnia severity, daytime sleepiness, sleep quality, and psychological strain (i.e., perceived stress and anxiety levels). Bioelectrical impedance and indirect calorimetry were used for body composition and resting metabolism assessment, respectively, while near-infrared spectroscopy and a graded cardiopulmonary exercise test were applied to determine peak oxygen uptake, ventilatory thresholds, muscle O 2 saturation, and maximal fat oxidation. Partial correlations and multiple regression analyses were used to explore associations between sleep disorders, fitness components, and physiological outcomes. Results: About 63% of athletes reported insomnia symptoms, with higher insomnia severity (effect size: 0.54, P = 0.04) and anxiety scores (effect size: 0.33, P = 0.03) in females. Insomnia severity was a significant negative predictor of the respiratory compensation point ( β = −0.09; P = 0.04), while the sleep quality index was inversely associated with the ventilatory threshold ( β = −0.63; P = 0.04), independent of sex and fitness level. No associations were found between sleep quality and disturbances with body composition, muscle O 2 saturation, or fat oxidation rates. Conclusion: Insomnia severity and poor sleep quality contribute to an impaired ventilatory efficiency during low-to-moderate intensity exercise, having no influence on cardiovascular fitness and metabolic flexibility. Thus, enhancing sleep hygiene may improve endurance training adaptations in athletes regardless of sex and fitness level.