Social jetlag is associated with cardiorespiratory fitness in male but not female adolescents

Abstract

IntroductionCardiorespiratory fitness (CRF) is a vital sign that can improve risk classification for adverse health outcomes. While lifestyle-related factors are associated with CRF, few have examined the influence of sleep characteristics, especially in youths. Social jetlag, a mismatch between one's biological clock and sleep schedule, is prevalent in adolescents and associated with increased adiposity, though its relationship with CRF is unclear. ObjectiveTo quantify the relationship between social jetlag and CRF, independent of other sleep characteristics. MethodsThis cross-sectional sample includes 276 New Zealand adolescents (14–18 years, 52.5% female). CRF (VO2max) was estimated from a 20-m multi-stage shuttle run. Average sleep duration, sleep disturbances, social jetlag, physical activity, and the number of bedroom screens were estimated from validated self-report surveys. Social jetlag is the difference in hours between the midpoint of sleep during weekdays (school) and weekend days (free). Combined and sex-stratified linear regression assessed the association between sleep outcomes and CRF, controlling for relevant covariates. ResultsMales slept 17.6 min less, had less sleep disturbances, and a 25.1-min greater social jetlag than their female peers (all p < 0.05). A 1-h increase in social jetlag was associated with a 0.72 ml/kg/min decrease in VO2max (95% CI: −1.31, −0.14), independent of other sleep variables, which were not associated with CRF. Sex-specific models indicated an association in males (B −0.93, 95% CI: −1.76, −0.09), but not females (B −0.32, 95% CI: −1.18, 0.55). ConclusionsSocial jetlag is negatively associated with CRF in adolescent males and may be a simple, measurable target for public health interventions.