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

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.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Redline reported receiving funding from Jazz Pharmaceuticals for an unrelated study of solriamfetol in adult obstructive sleep apnea.

Figures

Figure.. Association of Evening Chronotype Score and Social Jet Lag With Adiposity by Sex

A, Dual energy x-ray absorptiometry (DXA) fat mass index (P = .03 for interaction for chronotype and P = .01 for interaction for social jet lag). B, DXA trunk fat mass index (P = .02 for interaction for chronotype and P = .01 for interaction for social jet lag). C, Waist circumference (P = .04 for interaction for chronotype and P = .21 for interaction for social jet lag). D, Sum of skinfolds and triceps (P = .01 for interaction for chronotype and P = .02 for interaction for social jet lag). E, Body mass index z score (P = .02 for interaction for chronotype and P = .24 for interaction for social jet lag). F, Cardiometabolic risk z score (mean of 5 sex- and cohort-specific z scores for high-density lipoprotein cholesterol [inverted], log homeostatic model assessment of insulin resistance, log triglycerides, systolic blood pressure, and waist circumference; P = .23 for interaction for chronotype and P = .39 for interaction for social jet lag). Interaction P values are based on multivariable models before adding sleep as a covariate. Associations with adiposity measures are reported per additional point of evening preference on the inverted Morningness–Eveningness Scale for Children (higher scores indicate greater evening preferences, shown with circular markers and referred to as chronotype) and per 1 hour of social jet lag (difference in the mean sleep midpoint on weekend days minus the mean sleep midpoint on weekdays, shown with triangular markers). Blue markers indicate adjustment for adolescent age, pubertal status, race/ethnicity, season of measurement, maternal educational level, and household income; orange, “sleep-adjusted” markers indicate additional adjustment for actigraphy-measured sleep duration.