Background: An individuals chronotype, or preference in the timing of sleep or food intake, may have metabolic implications. Late chronotype has been associated with higher body mass index (BMI) and hemoglobin A1c (HbA1c) in adults and greater BMI, portion sizes, and lower HDL cholesterol levels in adolescents.
Objective and hypothesis: To examine associations between chronotype and risk factors for type 2 diabetes in children ages 1013 years. We hypothesize that late chronotype associates with greater insulin resistance and higher glucose levels.
Method: Ten (5 normal-weight (NW), 5 obese (OB)) preadolescents (age 11.4±0.5 years, Tanner stages 13) underwent anthropometric measurements and fasting blood draw; glucose, insulin, HbA1c, and lipid levels were measured. Obese participants underwent a 3-hour oral glucose tolerance test (OGTT). Mid-sleep time on free days (MSF), a measure of chronotype, was assessed via actigraphy over 1 week and secondarily through administration of the Childrens ChronoType Questionnaire (CCTQ) and Morningness-Eveningness Scale for Children (MESC).
Results: Sleep parameters did not differ significantly between NW and OB children. As expected, OB versus NW participants had significantly higher fasting plasma insulin levels (20.9±6.4 vs 4.2±2.6 μI/ml, P=0.002) and HOMA-IR levels (4.7±1.7 vs 0.9±0.6, P=0.004). MSF did not associate significantly with metabolic outcomes. HbA1c was positively associated with CCTQ chronotype score (r=0.64, P=0.047) and lower MESC score (r=−0.75, P=0.01), indicating later chronotype is associated with poorer glycemic control. HbA1c was also associated with overall time in bed (r=−0.84, P=0.005), later bedtimes overall (r=0.62, P=0.011) and on weekdays (r=0.81, P=0.002). On regression analysis, later weekday bedtime predicted a higher HbA1c independently of time in bed.
Conclusion: These preliminary findings suggest that a late chronotype in preadolescents may have a deleterious glycemic impact independent of bedtime duration and that advancing bedtimes may reduce glucose levels and lower risk of type 2 diabetes in preadolescents. Our preliminary findings call for expansion of our pilot study to a larger cohort.
10 Sep 2016 - 12 Sep 2016