The relationship between multiple sleep dimensions and obesity in adolescents: a systematic review

Background: The prevalence of obesity and sleep disruption in adolescents is increasing. Most adolescents experience a shift in their circadian rhythm during puberty, resulting in an evening circadian preference. Late-night screen usage, dietary choices, reduced mental well-being and early school schedules mean that adolescents are experiencing an increase in sleep disruption and social jetlag. Sleep disruption increases cortisol and decreases growth hormone levels, both of which are associated with obesity. The aim of this review was to systematically research the relationships between multiple objective adiposity measures and objective and subjective sleep measures. Methods: Ten bibliographic databases were searched for studies published up to August 2021, using search terms that included objective and subjective sleep or circadian rhythm measurements, objective adiposity measurements, and adolescents aged 8-18. Studies of adolescents with comorbidities or where only sleep duration or parent-reported sleep measures were examined were excluded. Eligible studies included adiposity measures as an outcome (dependent variable) and sleep or circadian measures (independent variables) as the exposure or vice versa. Results: A total of 41,146 studies were identified, 79 of which met the inclusion criteria. The studies were conducted in 27 countries and consisted of 63 cross-sectional studies, 12 longitudinal studies, 2 retrospective cohort studies and 2 intervention studies. Fifty-six different sleep measures and 15 adiposity measures were recorded. Sleep measures were categorised into five sleep dimensions- sleep efficiency, sleep quality, sleep timing, chronotype and other sleep characteristics. Chronotype, sleep timings, social jetlag and sleep habit measures were associated with high adiposity levels and obesity in adolescents. Conclusions: This review concludes that poor sleep hygiene, late chronotype and variability of and later sleep timings are consistently significantly associated with obesity and adiposity in adolescents. Furthermore, to understand the relationship between sleep quality and sleep efficiency with obesity and adiposity measures, more research should be completed. Additionally, more longitudinal research examining the relationship between the 5 sleep dimensions and obesity and adiposity in adolescents should be conducted. The findings of this review suggest an adaptation of an individual’s schedule to best suit chronotype preference and an improvement in sleep hygiene, including regular bedtimes and a consistent bedtime routine, could reduce adiposity levels and obesity in adolescents. Furthermore, reducing weight and adiposity in adolescents could help improve the individual’s sleep patterns and quality. Keywords: Adolescent Health; Circadian Rhythm; Obesity; Objective Adiposity Measure; Objective Sleep Measures; Overweight; Social Jetlag; Subjective Sleep Measures