Earlier wake time may lead to increased body fat mass in adolescents
Children may be more likely to gain fat mass if they have an earlier morning wake time, according to a speaker at ObesityWeek Interactive.
“This association between wake time and adiposity mostly complements previous data that indicates that sleep timing may be a particularly salient risk for adiposity development among youth,” Sarah LeMay-Russell, MS, a clinical researcher and fourth-year student at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, said during a presentation.
LeMay-Russell and colleagues analyzed data from 117 healthy youths aged 8 to 17 years (53.9% girls; 29.1% Black) who wore an actigraphy monitor continuously for 2 weeks. All participants provided data from at least 3 weekday nights of sleep and 1 weekend night of sleep. Weekend sleep was defined as taking place on Friday night into Saturday morning and Saturday night into Sunday morning.
Researchers compiled several statistics from the data, including sleep duration, sleep duration variability, weekend catch-up sleep, wake time and sleep midpoint time. Social jet lag, calculated as the midpoint of weekend sleep minus the midpoint of weekday sleep, and the shift in bed and wake time, calculated as weekend bed and wake times minus weekday bed and wake times, were also analyzed. Researchers used DXA to assess fat mass in participants at both baseline and at 1-year follow-up.
Participants slept for a mean of 7.2 hours (range, 4.9-8.8) per night, with an average bedtime of 11:32 p.m. (range, 8:52 p.m. to 3:21 a.m.) and a mean wake time of 7:56 a.m. (range, 4:55 a.m. to 11:37 a.m.) The average bedtime shift was 0.03 hours from the weekend to the weekday, the mean wake time shift was 0.05 hours, and the average social jet lag was 1 hour.
After adjusting for the time of year, age, sex, race, height, depression symptoms, and baseline fat mass, children who had an earlier mean wakeup time, an earlier average wakeup time on the weekends, and a greater waketime shift between the weekend and weekday, were more likely to have larger fat mass gains at follow-up. Sleep duration, sleep duration variability, bedtime, and bedtime shift were not associated with fat mass gains after 1 year.
LeMay-Russell said circadian rhythm misalignment may explain the association between wake time and fat mass.
“All organ systems in the body are regulated by the central circadian clock,” LeMay-Russell said. “This central clock is synchronized with external light and dark cycles, such as the sun. This clock produces predictable rhythms and bodily functions, such as hormone secretion. It’s possible that, if these participants were sleeping off their circadian rhythm, it impacted appetitive hormones, which are circadian in nature and could have resulted in this increased fat mass.”
LeMay-Russell added that more data are needed to further explore the association since sleep timing could be a modifiable target for reducing pediatric obesity.