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Original Investigation
September 16, 2019

Chronotype, Social Jet Lag, and Cardiometabolic Risk Factors in Early Adolescence

Author Affiliations
  • 1Division of Research, Kaiser Permanente Northern California, Oakland
  • 2Division of Chronic Disease Research Across the Lifecourse, Department of Population Medicine, Harvard Medical School, Harvard Pilgrim Health Care Institute, Boston, Massachusetts
  • 3Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Boston, Massachusetts
  • 4Division of Sleep Medicine, Harvard Medical School, Boston, Massachusetts
  • 5Department of Neonatology, University of Tübingen, Tübingen, Germany
  • 6Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
  • 7Division of General Academic Pediatrics, Massachusetts General Hospital for Children, Boston
JAMA Pediatr. 2019;173(11):1049-1057. doi:10.1001/jamapediatrics.2019.3089
Key Points

Question  Are chronotypes (evening vs morning preference) and social jet lag (sleep midpoint difference on weekends vs weekdays) associated with adiposity and cardiometabolic risk in young adolescents?

Findings  This cross-sectional study found that evening chronotypes and greater social jet lag were associated with greater adiposity in adolescent girls, but not boys, independent of sleep duration. There were no associations with a cardiometabolic risk score.

Meaning  This study suggests that female adolescents may be more vulnerable to the obesogenic effects of circadian misalignment; obesity prevention efforts should consider regular sleep-wake patterns in addition to sleep extension and sleep quality improvement.

Abstract

Importance  Inadequate sleep duration and quality increase the risk of obesity. Sleep timing, while less studied, is important in adolescents because increasing evening preferences (chronotypes), early school start times, and irregular sleep schedules may cause circadian misalignment.

Objective  To investigate associations of chronotype and social jet lag with adiposity and cardiometabolic risk in young adolescents.

Design, Setting, and Participants  Starting in 1999, Project Viva recruited pregnant women from eastern Massachusetts. Mother-child in-person visits occurred throughout childhood. From January 23, 2012, to October 16, 2016, 804 adolescents aged 12 to 17 years completed 5 days or more of wrist actigraphy, questionnaires, and anthropometric measurements. A cross-sectional analysis using these data was conducted from April 31, 2018, to May 1, 2019.

Exposures  Chronotype, measured via a continuous scale with higher scores indicating greater evening preferences, and social jet lag, measured as the continuous difference in actigraphy sleep midpoint in hours from midnight on weekends vs weekdays, with higher values representing more delayed sleep timing on weekends.

Main Outcomes and Measures  Adiposity, measured via anthropometry and dual-energy x-ray absorptiometry. For a subset of 479 adolescents with blood samples, cardiometabolic risk scores were computed as the mean of 5 sex- and cohort-specific z scores for waist circumference, systolic blood pressure, inversely scaled high-density lipoprotein cholesterol, and log-transformed triglycerides and homeostatic model of insulin resistance.

Results  Among the 804 adolescents in the study, 418 were girls and 386 were boys, with a mean (SD) age of 13.2 (0.9) years. In multivariable models adjusted for age, puberty, season, and sociodemographics, associations of chronotype and social jet lag with adiposity varied by sex. For girls, greater evening preference was associated with a 0.58-cm (95% CI, 0.12-1.03 cm; P = .04 for interaction) higher waist circumference and 0.16 kg/m2 (95% CI, 0.01-0.31 kg/m2; P = .03 for interaction) higher fat mass index as measured by dual-energy x-ray absorptiometry; each hour of social jet lag was associated with a 1.19-cm (95% CI, 0.04-2.35 cm; P = .21 for interaction) higher waist circumference and 0.45 kg/m2 (95% CI, 0.09-0.82 kg/m2; P = .01 for interaction) higher fat mass index as measured by dual-energy x-ray absorptiometry. Associations of social jet lag and evening chronotypes persisted for many measures of adiposity after adjustment for sleep duration and other lifestyle behaviors. By contrast, no associations were observed in boys. There were no associations with the cardiometabolic risk score for either sex, although statistical power was low for this outcome.

Conclusions and Relevance  Evening chronotypes and social jet lag were associated with greater adiposity in adolescent girls but not adolescent boys. Interventions aimed at improving sleep schedules may be useful for obesity prevention, especially in girls.

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