Research background: The connection between sleep health, circadian timing of sleep and insulin sensitivity in adolescents with obesity
More than 33% of adolescents in the U.S. are obese and at risk for comorbid health conditions such as type 2 diabetes. Insulin resistance is more common in adolescents with obesity and is a risk factor for poor health consequences.
Adolescents experience a delay in circadian rhythms due to both physiological and environmental influences, yet often have to wake early for school resulting in insufficient sleep.
Though researchers have found a connection between short and delayed sleep and insulin resistance in adults, they have not studied it extensively in adolescents. Stacey L. Simon, PhD, and other researchers sought to study the relationship between insulin resistance and sleep health in adolescents with obesity.
Research methods: Measuring circadian rhythm and blood glucose in adolescents with obesity
The researchers recruited study participants between September 2014 and May 2017 from weight management and specialty clinics at Children's Hospital Colorado. All participants were habitually sedentary and in late puberty. Those with diabetes or anemia or those who were taking medications impacting insulin resistance or sleep were excluded from the study.
During this study, participants wore an actigraphy monitor, a watch-like device worn on the wrist that measures sleep duration and timing. Researchers assessed their insulin sensitivity with fasting labs and a three-hour oral glucose tolerance test.
The study participants stayed overnight at Children's Colorado's Clinical and Translational Research Center and provided saliva samples every 30 to 60 minutes to measure melatonin levels, a marker of circadian rhythm. The researchers kept participants in dim light throughout the visit to avoid the impact of light exposure on melatonin.
Research results: Study participants experienced insufficient sleep
Overall, participants averaged less than 7.5 hours of sleep per night on weekend and weekday nights, which represents insufficient sleep compared to the 8 to 10 hours recommended for adolescents.
Actigraphy and insulin sensitivity
Researchers found that a longer total sleep time and more time in bed during the week and weekend, as well as an earlier weekday bedtime, were associated with better insulin sensitivity.
When comparing participants that slept less than 6.6 hours per night with those who slept at least 6.6 hours per night, researchers found that participants with more sleep had better insulin sensitivity.
Melatonin and insulin sensitivity
Better alignment between measures of circadian rhythms and actual bedtimes and wake times was associated with better insulin sensitivity.
Research discussion: Lack of sleep associated with insulin resistance in adolescents with obesity
Researchers found that the participants with more sleep and more time in bed in general, as well as earlier bedtimes during the week, had better insulin sensitivity. Sleep at a later circadian time was associated with insulin resistance.
The school night sleep duration of study participants was approximately 1.5 hours less than the minimum recommended for adolescents. Short sleep duration was associated with impaired insulin sensitivity.
This is likely the first study to use salivary melatonin as an objective measurement of circadian rhythm to examine associations with insulin sensitivity in adolescents.
Researchers found significant differences in actigraphy variables between sleep on weekdays and weekends in the cohort. The cohort may have experienced a weekend phase delay or social jet lag (when sleep patterns are different on the weekends than they are during the week).
Research conclusion: Improving sleep and metabolic health in adolescents
Clinicians and researchers should be aware of the potential for sleep and circadian rhythm disturbances and the link to negative health consequences, particularly for adolescents with obesity. Additional research is necessary to determine if sleep and circadian interventions, and possible later school start times, could improve metabolic health for this population.
The study was presented at the 2018 SLEEP conference in Baltimore, Maryland, and published in the Nov. 19, 2018, issue of The Journal of Pediatrics.
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