Research has shown a link between poor sleep health and late circadian timing with cardiometabolic health in adolescents with type 1 diabetes (T1D). Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in T1D, which begins as early as adolescence, and current therapies are limited. Therefore, this study plans to investigate whether cardiometabolic health can be improved with increased sleep duration and advanced circadian timing in adolescents with T1D with habitually insufficient sleep. To answer this question, investigators will study adolescents with T1D who get <7h sleep on school nights and measure changes in insulin sensitivity, glycemic control, and vascular function after one month of a sleep and circadian intervention (1+ hour longer time in bed each night plus evening melatonin and morning light therapy) compared to one month of typical sleep (usual school schedule).

Inclusion Criteria:

• High school students between the ages of 14-19 years;
• Diagnosed with T1D for ≥1 year;
• Using an insulin pump or other automated insulin delivery system;
• Have typically insufficient sleep, defined by ≤ 7 h per night on school days (assessed by actigraphy);
• With or at risk for obesity based on either above-average weight (BMI ≥50th percentile) or parental history of obesity (BMI ≥ 30 kg/m2);
• Tanner stage 4 or 5, based on breast development for girls and testicular size for boys.

Exclusion Criteria:

• Prior diagnosis of a sleep disorder (e.g., insomnia, obstructive sleep apnea) or an elevated screening score on the OSA subscale of the Sleep Disorders Inventory for Students-Adolescents measure
• Regular use of medications affecting sleep (e.g., stimulants, atypical antipsychotics, melatonin or other sleep aids);
• Regular use of medications affecting IR (systemic steroids, adjunctive diabetes medications);
• HbA1c ≥12%;
• Severe illness or DKA within 60 days;
• IQ<70 or severe mental illness impacting sleep or ability to participate in the study;
• Night-shift employment or other obligations that would preclude adherence to the intervention.

All fully deidentified raw and processed/scored data will be shared.

Access to the data will be made at the end of the grant award or when a publication has been submitted. Once the data are submitted, the archive will control the long-term persistence of the data set.