Experimental Changes in Children's Sleep Duration and Timing: Effect on Obesity and Type 2 Diabetes Risk

Eligible families who provide consent/assent will be enrolled into a five week study. All families will complete assessments at baseline, two weeks and four weeks. Each assessment lasts one week and children will be asked to wear an actigraph on their wrist (to measure sleep) and an accelerometer on their hip (to measure physical activity). At the end of the week families will be scheduled for a visit at the research center first thing in the morning approximately one hour after waking and following an overnight fast. During this visit, actigraphs and accelerometers will be downloaded and data will be reviewed with families. Children will be weighed and measured for height and have their body composition assessed. To measure glucose regulation, children will first have 5 ml of blood drawn in a fasted state. They will then ingest a glucose solution (1.75 g/kg; maximum of 75 g) over 2 minutes, and blood will be drawn (1.5 ml) 120 min after the child consumes the solution. At week 4, 5 ml blood will be drawn fasting; OGTT will not be administered (see note below). Research staff will also complete one-day dietary recalls with participants at each center-based assessment to obtain information on all foods consumed over the previous 24-hour period. In addition, at the baseline assessment only, parents will complete questionnaires on basic demographic information and child sleep. It is anticipated that the total time for each assessment will take approximately 2.5-3 hours (1 hour at 4 weeks). Following eligibility confirmation at the baseline assessment, families will be randomized to one of four protocols: 1) Enhance TIB by 90 min/night; 2) Enhance TIB by 45 min/night; 3) Regularize Sleep Schedule; or 4) Typical Sleep Schedule.

Continuous glucose monitoring In a voluntary subset of randomly selected children (approximately n = 4/group) 72-hour continuous glucose monitoring (CGM) will be performed. If the child and family agree to participate in CGM, they will come to the Center for an additional visit during which a disposable subcutaneous glucose-sensing device connected to a battery-operated recorder will be inserted subcutaneously (a thin tube under the surface of the skin). This sensor measures glucose every ten seconds and records an average value every five minutes.