In what is believed to be the first study of its kind to measure circadian rhythm as a factor in insulin sensitivity in adolescents, researchers at Children's Hospital Colorado have uncovered a link between sleep quality and insulin resistance. Specifically, researchers found shorter sleep duration, later weekday bedtimes and later circadian timing of sleep were associated with reduced insulin sensitivity in teenagers during the school year. And insulin resistance is a risk factor for developing type 2 diabetes and other related health conditions.
"Traditionally, we've really only thought about healthy lifestyle behaviors as things like diet and exercise,' says Stacey Simon, Ph.D., pediatric sleep psychologist at the Breathing Institute at Children's Colorado and lead author of the study. "This study shows we need to consider our sleep and circadian rhythm as an important health behavior as well."
Quantity of sleep important, but so is timing
Simon and her team of researchers at Children's Colorado measured the sleep habits of 31 overweight and obese adolescents in the study using actigraphy monitors that subjects wore on their wrists for a week at home. They then measured participants' insulin sensitivity and captured melatonin levels—a marker of circadian rhythm—in the teens' saliva during an overnight stay at Children's Colorado's Clinical and Translational Research Center.
The study results showed a direct correlation between the amount of sleep participants got and their insulin sensitivity. But the research showed quantity of sleep only told part of the story—it's also important when adolescents are sleeping. Participants whose sleep patterns better aligned with their circadian rhythms also showed better insulin resistance.
Help through better sleep routines, later school starts?
Simon says teenagers' circadian rhythms naturally tend toward later nights than younger children. She says her research supports an American Academy of Pediatrics recommendation for later start times for high schools.
"We're seeing more research that shows delaying school start times has a positive impact for adolescents in terms of academics and mental health,' Simon says. "But this study shows it may potentially affect their physical health as well. Allowing adolescents the opportunity to not only get sufficient sleep but also to sleep according to their bodies' internal clocks may be beneficial for their health.'
There are also steps health care practitioners and parents can take to improve adolescents' metabolic health through improved sleep patterns, according to Simon:
- Inquire. Ask about sleep patterns during routine checkups—not just how much sleep, but when.
- Emphasize. Make quality sleep a priority on level with other healthy activities.
- Enforce. Observe structured, regular bedtimes—even on the weekends.
- Remove. Eliminate electronics from the bedroom to help facilitate healthy sleep.
Additional research underway
Simon says further research is needed to better understand the relationship between sleep and metabolism in adolescents. Her team is working on a study with high school students who are getting insufficient sleep on school nights. The ongoing research measures insulin sensitivity and other health markers after one week of their regular sleep and then compares those levels following a week of improved sleep. The goal: to see if the markers show improvement following the week of better sleep.