Relationship Between Sleep Duration,Obesity And Obesity-related Hormones In Children

BackgroundObesity is now reaching epidemic proportions both in childhood and adolescents and has become the most prevalent nutritional disease in the world.Childhood obesity associates with the incidence of cardio-cerebral-vascular disease,metabolic syndrome(MS),cancer and death in their adulthood.It has become a concerned social problem.Therefore,prevention and/or treatment of childhood and adolescent obesity offers the best hope of preventing adult obesity and its related morbidities.So far,we have not known the precise pathological and physiological mechanism of obesity;particularly for the obesity in children,there is no better method to manage it except diet-control and exercise.The newest evidence showed that insufficient sleep could cause obesity by changing dietary behavior and reducing energy consumption to consequently inducing imbalance of energy metabolism in human body.Several recent large researches reported that a U-shaped curvilinear relationship was observed between sleep duration and obesity in adults and a negative relation in children and such difference may be related to Orexin,Leptin and Ghrelin (three key hormones in appetite regulation).As the sleep duration of children is an easy-to-adjust risk factor,to study its relationship to obesity would be significant to prevent and treat obesity in children.Unfortunately,in China,any epidemioiogical survey on sleep duration among obese children has not been carried out yet,nor any research on whether insufficient sleep would increase the incidence of obesity-related complications or have a relation to appetite regulatory hormones.Objective:This study was designed to investigate the relation of sleep duration,insufficient sleep to obesity and its complications in children and adolescents in Zhejiang Province and to explore the underlying mechanism.Methods1.Epidemiological survey was carried out through questionnaires."Life Style of Healthy Children in Zhejiang Province" was handed out to 338 children with normal body mass index (BMI)and "Life Style and Sleep Diaries of Obese Children" to 391 obese children;they were at the equivalent age.Difference in self-reported sleep time was compared and factors for obesity were analyzed.2.Anthropometry was used to measure height,weight,waist circumference(WC),hip circumference and blood pressure in all subjects.3.Laboratory tests were used to determine fasting blood glucose(FBG),fasting insulin(FINS),liver enzymes and blood lipid profile;glucose tolerance test and releasing test of insulin were conducted to assess the relation of chronic insufficient sleep to obesity and its complications in obese children;double antibodies sandwich ELISA method was used to detect serum Leptin,Ghrelin and Orexin with commercial reagent kits to explore whether changes in these markers were related to sleep duration and obesity.Results1.Findings from epidemiological survey1.1 Sleep duration of obese and healthy children On average,obese children slept (8.66±1.00)h,which was 1 h less than the control group did(9.70±0.83)h.Sleeping hours was shortened with the increase of age;15.60%of obese children slept less than 8 h compared to 0.89%of the control children;In the obese children with BMI≥30 kg/m~2,shorter sleep duration(8.10±0.97)h was observed than that(8.83±0.76)h in those with BMI＜30 kg/m~2.1.2 Short habitual sleep time:a risk factor for obesity Multiple variable logistic analysis showed that children sleeping less was susceptible to be obese,especially those sleeping less than 8 h.Compared to them,the odds ratio was 0.015(95%confidence interval:0.005-0.051) for the children sleeping more than 10 h.2.Effect of sleep duration on BMI,Leptin,Ghrelin and Orexin All subjects were divided into 2 groups:subjects in Group 1 was diagnosed as having sleep loss;Group 2 was in the absence of this problem.BMI,Leptin,Ghrelin and Orexin were higher in Group 1 than that in Group 2.Linear regression analysis found that the levels of the above serum markers were elevated as the sleep duration decreased and in the children with higher BMI.Compared to those sleeping 10 and more than 10 h,BMI,Ghrelin and Orexin in the obese children sleeping less than 8 h increased by 18.97%,58.74%,and 34.62%,respectively.3.Effect of sleep duration on MS The incidence of MS among obese children was 19.44%; 74.68%(292/391)obese children were with at least one abnormal diagnosing parameter for MS.Logistic regression analysis using unordered categorical variables revealed that sleep duration is the risk factor for MS with an odds ratio of 0.492(95%confidence interval: 0.395-0.782),that is,short sleep was associated with high incidence of MS.The abnormal parameters for diagnosing MS were different between Group 1 and 2(P＜0.05);the difference was more obvious in patients sleeping less than 8 h.4.Obesity in childhood and insulin resistance Multiple linear regression model analysis showed that BMI bore a relation to HOMA-IR and HOMA-IS(P＜0.05),one unit increase in BMI accompanied by 0.261 and 11.054 increase in HOMA-IR and HOMA-IS,respectively.Conclusion1.Sleep loss is common.On average,obese children sleep 1 h less than those with normal BMI and the difference will be enlarged as the abnormality in BMI extends.2.In children with short sleep,BMI and serum Leptin,Ghrelin and Orexin is elevated; Compared to those sleeping 10 and more than 10 h,BMI,Ghrelin and Orexin in the obese children sleeping less than 8 h were increased;increased BMI is associated with high Leptin, Ghrelin and Orexin,particular in those with less than 8 h sleep;Leptin resistance has been observed in children with sleep loss and is inversely related to the reduction of sleep duration. The Leptin level is elevated as BMI increases,which indicates that the former is related to simple obesity in childhood. 3.Chronic sleep restriction is associated with obesity-related complications;thus,it is one of the risk factors for MS and is highly linked to every component of MS.