Sleep Timing and Insulin Resistance in Adolescents With Obesity
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This study examines the relationship between sleep timing and insulin resistance in adolescents with obesity. The investigators also aim to develop a physiologically-based mathematical model of adolescent sleep/wake and circadian interactions.
Dim Light Melatonin Onset and Offset [ Time Frame: 1 day ]
~1mL saliva was collected at 30- to 60- minute intervals in dim light (<5 lux in the angle of gaze, approximately the light level of candlelight or civil twilight) from approximately 5pm until noon the next day. Dim light melatonin onset (DLMOn) was defined as the linear interpolated clock time at which evening salivary melatonin concentrations increased and remained above a threshold of 3pg/mL. Melatonin offset (DLMOff) was the linear interpolated clock time at which salivary melatonin concentrations fell below this threshold. Later DLMOn and DLMOff are indicative of a later circadian rhythm.
Insulin Sensitivity [ Time Frame: 3 hours ]
After an overnight fast, participants completed an oral glucose tolerance test (OGTT) in the morning. Participants consumed a 75g dextrose drink and serum for glucose and insulin concentrations were collected at baseline and every 30 minutes for 3 hours. The homeostatic model assessment for insulin resistance (HOMA-IR) was calculated as [fasting insulin (μU/ml) x fasting glucose (mmol/l)] / 22.5); lower HOMA-IR indicates better insulin sensitivity. The Matsuda Index was calculated as √10,000 / [[fasting insulin (μU/ml) x fasting glucose (mmol/l)] x [mean OSTT insulin (μU/ml) x mean OSTT glucose (mmol/l)]]; high Matsuda Index indicates better insulin sensitivity.
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Layout table for eligibility information
Ages Eligible for Study:
15 Years to 19 Years (Child, Adult)
Sexes Eligible for Study:
Accepts Healthy Volunteers:
Adolescents with obesity
High school students between the ages of 15-19
BMI > 90th percentile
Tanner stage 2 or greater
Any medications that affect insulin resistance or sleep (e.g., metformin, hormonal contraception, stimulants, atypical antipsychotics)
Regular use of melatonin or sleep aids
A prior diagnosis of obstructive sleep apnea, diabetes (HbA1c > 6.5), liver disease other than non-alcoholic fatty liver disease, pregnancy or breastfeeding
IQ < 70 or severe mental illness that may impact sleep (e.g., schizophrenia, psychotic episodes)
Not enrolled in a traditional high school academic program (e.g., home school students)
Night shift employment
Travel across more than 2 time zones in the month prior to the study