Effect of late bedtime on salivary glucose and abdominal obesity in children

Inadequate sleep has negative effect on health including obesity, diabetes, and cardiovascular diseases. Current evidence showed that delayed night sleep may impair endocrine function, disrupt glucose metabolism and promote abnormal weight gain, irrespective of caloric intake. The aim of this analysis was to investigate the longitudinal relation between bedtime, salivary glucose levels, and waist circumference among Kuwaiti children. Repeated measures data were collected from 6316 children 8-14 years old at two time points: 2012 and 2014. Children were approximately equally distributed among 138 elementary schools representing the six governorates of Kuwait. Trained examiners conducted body weight measurements, sleep evaluation interviews, and collected saliva samples. Mixed-effect multivariate linear regression model was conducted to determine the longitudinal relationship between bedtime and the rate of change in abdominal obesity. Other explanatory variables, mediator, or potential confounders assessed were glucose level (> 1.13 mg/dL), systolic blood pressure, fitness, ethnicity, and gender. There was a significant increase of waist circumference with later bedtime over time (P < 0.05). A higher salivary glucose level (higher than 1.13 mg/dL) was a positive partial mediator in the relation between bedtime and waist circumference. There were statistically significant variations between schools across time (P < 0.05). Longitudinal analysis of Kuwaiti children revealed that going to bed late increases salivary glucose (and presumably plasma glucose) and predicts abdominal obesity in Kuwaiti children with strong clustering effect within schools over time.