Increasing evening chronotypes and social jet lag are associated with increased adiposity in adolescent girls, according to study results published in JAMA Pediatrics.
The researchers did not find any associations between sleep timing and adiposity in adolescent boys.
Data from Project Viva, a longitudinal birth cohort study that recruited pregnant women from eastern Massachusetts starting in 1999, were used for this cross-sectional study. Mother-child in-person visits took place throughout childhood and early adolescence. The researchers used data from 804 children and adolescents (mean age, 13.2±0.9 years) from January 2012 to October 2016. During this period, patients completed ≥5 days of wrist actigraphy, sleep questionnaires, and anthropometric measurements.
The researchers measured chronotype with a continuous scale in which higher scores indicated greater evening preferences. They measured social jet lag as the continuous difference in actigraphy sleep midpoint in hours from midnight on weekends compared with weekdays. Higher values of social jet lag indicated more delayed sleep timing on weekends.
The study’s primary outcome was adiposity, which the researchers measured via anthropometry and dual-energy x-ray absorptiometry. The researchers computed cardiometabolic risk scores for a subset of patients who provided fasting blood samples (n=479). To determine the score, they calculated 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.
After adjusting for age, pubertal status, season, and sociodemographics, the results indicated that associations of chronotype and social jet lag with adiposity varied by sex, as the researchers had hypothesized.
Among adolescent girls, greater evening preference was associated with a 0.58-cm higher waist circumference (95% CI, 0.12-1.03 cm; P =.04 for interaction) and 0.16 kg/m2 higher fat mass index (95% CI, 0.01-0.31 kg/m2; P =.03 for interaction).
An hour of social jet lag was associated with a 1.19 cm higher waist circumference (95% CI, 0.04-2.35 cm; P =.21 for interaction) and 0.45 kg/m2 higher fat mass (95% CI, 0.09-0.82 kg/m2; P =.01 for interaction) in adolescent girls.
The researchers did not find any significant associations between social jet lag and evening chronotypes with adiposity in adolescent boys, but the associations generally followed the same patterns as those observed in girls.
In the subset of patients who provided blood samples, the researchers did not find any associations with cardiometabolic risk score and sleep timing in either sex.
“Regular sleep-wake patterns and earlier bed-wake times may extend sleep duration, reduce social jet lag, and benefit adolescents’ cardiometabolic health,” the researchers wrote.
Feliciano EMC, Rifas-Shiman SL, Quante M, Redline S, Oken E, Taveras EM. Chronotype, social jet lag, and cardiometabolic risk factors in early adolescence [published online September 16, 2019]. JAMA Pediatr. doi:10.1001/jamapediatrics.2019.3089