Dorit Koren

Sleep Architecture and Glucose and Insulin Homeostasis in Obese Adolescents

OBJECTIVE Sleep deprivation is associated with increased risk of adult type 2 diabetes mellitus (T2DM). It is uncertain whether sleep deprivation and/or altered sleep architecture affects glycemic regulation or insulin sensitivity or secretion. We hypothesized that in obese adolescents, sleep disturbances would associate with altered glucose and insulin homeostasis. RESEARCH DESIGN AND METHODS This cross-sectional observational study of 62 obese adolescents took place at the Clinical and Translational Research Center and Sleep Laboratory in a tertiary care children’s hospital. Subjects underwent oral glucose tolerance test (OGTT), anthropometric measurements, overnight polysomnography, and frequently sampled intravenous glucose tolerance test (FSIGT). Hemoglobin A1c (HbA1c) and serial insulin and glucose levels were obtained, indices of insulin sensitivity and secretion were calculated, and sleep architecture was assessed. Correlation and regression analyses were performed to assess the association of total sleep and sleep stages with measures of insulin and glucose homeostasis, adjusted for confounding variables. RESULTS We found significant U-shaped (quadratic) associations between sleep duration and both HbA1c and serial glucose levels on OGTT and positive associations between slow-wave sleep (N3) duration and insulin secretory measures, independent of degree of obesity, pubertal stage, sex, and obstructive sleep apnea measures. CONCLUSIONS Insufficient and excessive sleep was associated with short-term and long-term hyperglycemia in our obese adolescents. Decreased N3 was associated with decreased insulin secretion. These effects may be related, with reduced insulin secretory capacity leading to hyperglycemia. We speculate that optimizing sleep may stave off the development of T2DM in obese adolescents.

Metabolic and Glycemic Sequelae of Sleep Disturbances in Children and Adults

The prevalence of obesity in adults and children has increased greatly in the past three decades, as have metabolic sequelae, such as insulin resistance and type 2 diabetes mellitus (T2DM). Sleep disturbances are increasingly recognized as contributors to this widespread epidemic in adults, and data are emerging in children as well. The categories of sleep disturbances that contribute to obesity and its glycemic co-morbidities include the following: (1) alterations of sleep duration, chronic sleep restriction and excessive sleep; (2) alterations in sleep architecture; (3) sleep fragmentation; (4) circadian rhythm disorders and disruption (i.e., shift work); and (5) obstructive sleep apnea. This article reviews current evidence supporting the contributions that these sleep disorders play in the development of obesity, insulin resistance, and T2DM as well as possibly influences on glycemic control in type 1 diabetes, with a special focus on data in pediatric populations.

Role of sleep quality in the metabolic syndrome

Emerging evidence has assigned an important role to sleep as a modulator of metabolic homeostasis. The impact of variations in sleep duration, sleep-disordered breathing, and chronotype to cardiometabolic function encompasses a wide array of perturbations spanning from obesity, insulin resistance, type 2 diabetes, the metabolic syndrome, and cardiovascular disease risk and mortality in both adults and children. Here, we critically and extensively review the published literature on such important issues and provide a comprehensive overview of the most salient pathophysiologic pathways underlying the links between sleep, sleep disorders, and cardiometabolic functioning.

Adiponectin Is Associated with Favorable Lipoprotein Profile, Independent of BMI and Insulin Resistance, in Adolescents

CONTEXT Children with obesity and insulin resistance (IR) have decreased adiponectin and have increased cardiovascular risk. Adiponectin has antiatherogenic effects, but its mechanism is unclear. OBJECTIVES Our objectives were 1) to compare lipoprotein subclass particles among obese and lean adolescents and delineate their relationships with IR and 2) to measure relationships between adiponectin and lipoproteins and their dependence on body mass index (BMI) and/or IR. DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURES: This was a cross-sectional study of 57 obese and 38 lean pubertal adolescents, measuring lipoprotein subclass particles (nuclear magnetic resonance spectroscopy), lipids, adiponectin, and homeostasis model assessment of IR (HOMA-IR). RESULTS Obese had higher low-density lipoprotein (LDL) cholesterol (P = 0.018), higher small LDL particles (LDL-P) (P < 0.0005), smaller LDL-P size (P < 0.0005), smaller high-density lipoprotein particle (HDL-P) size (P < 0.0005), lower HDL cholesterol (HDL-C) (P < 0.0005), and higher small HDL-P (P = 0.009) compared with lean. HOMA-IR was higher in obese than lean (P < 0.0005) and positively associated with triglycerides, large very LDL-P, and small HDL-P and negatively with HDL-P size in obese. Adiponectin was lower in obese than lean (P < 0.0005) and was positively associated with LDL-P size, HDL-P size, and HDL-C and negatively with triglycerides, small LDL-P, large very LDL-P, and small HDL-P in obese. Using linear regression adjusting for demographics, Tanner stage, BMI, and HOMA-IR in all adolescents, adiponectin was positively associated with LDL-P size (P = 0.028), HDL-P size (P < 0.0005), and HDL-C (P = 0.042) and negatively with small LDL-P (P = 0.009) and small HDL-P (P = 0.004). CONCLUSIONS Obese adolescents have lower adiponectin levels than lean, and a more atherogenic lipoprotein profile, associated with increased IR. Adiponectin was inversely associated with atherogenic lipoproteins in adolescents, even after adjusting for obesity and IR. This is the first such report in children, and suggests a relationship between adiponectin and lipoproteins in adolescents independent of BMI and IR.

Impact of obstructive sleep apnoea on insulin resistance in nonobese and obese children.

Obstructive sleep apnoea (OSA) has been inconsistently associated with insulin resistance and adverse metabolic states. We aimed to assess independent contributions of OSA to insulin resistance and dyslipidaemia in a large paediatric cohort. Habitually snoring children underwent overnight polysomnography, anthropometric measurements and fasting laboratory evaluations. Primary outcome measures included insulin, glucose, homeostasis model of insulin resistance, lipoproteins and sleep disturbance measures. Among 459 children aged 5–12 years, obesity was the primary driver of most associations between OSA and metabolic measures, but sleep duration was inversely associated with glucose levels, with N3 and rapid eye movement (REM) sleep being negatively associated and sleep fragmentation positively associated with insulin resistance measures. In children with mild OSA, the presence of obesity increased the odds for insulin resistance, while higher apnoea/hypopnoea index values emerged among obese children who were more insulin-resistant. The exclusive presence of interactions between OSA and obesity in the degree of insulin resistance is coupled with synergistic contributions by sleep fragmentation to insulin resistance in the context of obesity. Insufficient N3 or REM sleep may also contribute to higher glycaemia independently of obesity. Studies are needed to better delineate the roles of puberty and sleep fragmentation in insulin resistance and the metabolic syndrome. OSA and obesity jointly affect insulin resistance, but insulin resistance is absent in nonobese children with OSA http://ow.ly/W4BmY

Impact of Adenotonsillectomy on Insulin Resistance and Lipoprotein Profile in Nonobese and Obese Children

BACKGROUND OSA associates with insulin resistance (IR), hyperglycemia, and dyslipidemia consistently in adults, but inconsistently in children. We set out to quantify the impact of OSA treatment upon obesity and metabolic outcomes and thus assess causality. METHODS Sixty-nine children with OSA; mean age, 5.9 years (range, 3-12.6); 55% boys; and 68% nonobese (NOB) underwent baseline overnight polysomnography, anthropometric and metabolic measurements, adenotonsillectomy (T&A), and follow-up testing a mean 7.9 months (range, 2-20) later. RESULTS Fifty-three children (77% of study cohort; 91% of obese children) had residual OSA (apnea-hypopnea index > 1 event/h) post-T&A. Fasting plasma insulin (FPI, 14.4 ± 9.4 → 12.6 ± 9.7 μIU/mL, P = .008), homeostasis model assessment-IR (3.05 ± 2.13 → 2.62 ± 2.22, P = .005), and high-density lipoprotein (HDL) (51.0 ± 12.9 → 56.5 ± 14.4 mg/dL, P = .007) improved despite increased BMI z score (1.43 ± 0.78 → 1.52 ± 0.62, P = .001); changes did not differ significantly between sexes or NOB and obese participants; however, post-T&A BMI z score rather than apnea-hypopnea index was the main predictor of levels of follow-up FPI, HDL, and other metabolic parameters. Higher baseline FPI and BMI-z predicted likelihood of residual OSA; conversely, on regression analysis, follow-up IR, HDL, and triglycerides were predicted by BMI z score, not residual OSA. CONCLUSIONS T&A improved IR and HDL, and residual OSA is predicted by baseline FPI and BMI z score, indicating a causal relationship; however, following T&A, residual metabolic dysfunction related to underlying adiposity rather than remaining sleep-disordered breathing. Finally, T&A cured OSA in < 25% of all children and only 10% of obese children; post-T&A polysomnography is indicated to assess which children still require treatment.

Prevalence of Periodic Limb Movements during Sleep in Normal Children

STUDY OBJECTIVES Although the American Academy of Sleep Medicine (AASM) mandates that periodic limb movements during sleep (PLMS) be scored on every polysomnogram, and considers a periodic limb movement index (PLMI) > 5/h abnormal in children, there is a lack of community-derived data regarding the prevalence of PLMS in children, and no data to support this cutoff value. Therefore, the aim of this study was to determine the prevalence of PLMS in a sample of normal children. DESIGN Retrospective study. PARTICIPANTS 195 healthy, non-snoring children aged 5-17 years, recruited from the community, who underwent polysomnography for research purposes. METHODS PLMS were scored using the AASM 2007 criteria. MEASUREMENTS AND RESULTS The group age (median [IQR]) was 12.9 [10-15] years, and 58% were male. Sleep architecture was normal, and the obstructive apnea hypopnea index was 0.1 [0-0.3]/h. The median PLMI was 0/h, ranging from 0 to 35.5/h. Fifteen (7.7%) subjects had a PLMI > 5/h, and only 3 (1.5%) met the adult pathologic criterion of more than 15/h. Use of the 95th percentile PLMI cutoff of 7.2/h produced little difference in categorization between groups. Children with a PLMI > 5/h had a higher arousal index than those with a lower PLMI (11.6 [8.8-14.6] vs 8.1 [6.1-9.9]/h, respectively, P = 0.003). CONCLUSIONS This study provides normative data to the field and supports the clinical periodic limb movement index cutoff of > 5/h based on both prevalence and the correlate of increased sleep fragmentation. Periodic limb movements during sleep are infrequent in normal children recruited from the community. CITATION Marcus CL, Traylor J, Gallagher PR, Brooks LJ, Huang J, Koren D, Katz L, Mason TB, Tapia IE. Prevalence of periodic limb movements during sleep in normal children.

Anthropometric predictors of visceral adiposity in normal‐weight and obese adolescents

Obesity and fat distribution patterns [subcutaneous vs. visceral adipose tissue (VAT)] are important predictors of future cardiometabolic risk. As accurate VAT measurement entails imaging, surrogate anthropometric measurements that would be cheaper and quicker to obtain would be highly desirable. Sagittal abdominal diameter (SAD) may be better than other VAT surrogate measures in adults, but the value of SAD to predict magnetic resonance imaging (MRI)‐determined VAT in adolescents of different races, sexes, and pubertal stages has not been determined.

Interrelationships between obesity, obstructive sleep apnea syndrome and cardiovascular risk in obese adolescents

Background/Objectives:Obstructive sleep apnea syndrome (OSAS) may be a cardiovascular disease (CVD) risk factor independently of obesity in adults. Pediatric studies have associated OSAS with endothelial dysfunction, but few studies have examined relationships between OSAS and macrovascular sequelae. Our objective was to examine OSAS’s independent contribution to macrovascular CVD risk measures in obese adolescents.Subjects/Methods:This cross-sectional observational study was conducted at Children’s Hospital of Philadelphia Clinical Research and Academic Sleep Centers, and University of Pennsylvania Vascular Research Unit. Thirty-one obese non-diabetic adolescents underwent anthropometric measurements, overnight polysomnography, fasting laboratory draw and cardiovascular imaging. Cardiovascular outcome measures included maximal carotid intima–media thickness (cIMTmax), a measure of carotid structural changes, and carotid-femoral pulse wave velocity (CFPWV), an aortic stiffness measure whose relationship vis-à-vis OSAS in children has not been previously examined. Carotid diameter and augmentation index (AIx, measuring central pressure augmentation from wave reflections) were assessed. Potential confounding variables examined included blood pressure, lipoproteins, high-sensitivity C-reactive protein, insulin and glucose.Results:The apnea hypopnea index, a primary OSAS measure, was not associated with cIMTmax, carotid diameter, CFPWV or AIx. body mass index (BMI) associated positively with cIMTmax (r=0.52, P=0.006) and CFPWV (r=0.45, P=0.01). Mean asleep end-tidal CO2 was negatively associated with carotid diameter (r=−0.63, P<0.0005). Insulin levels were negatively associated with AIx (r=−0.53, P=0.02).Conclusions:OSAS did not predict carotid structural changes or arterial stiffness independently of BMI in obese adolescents. Higher insulin levels associated with lower central pressure wave augmentation. Finally, long-term hypercapnia may predispose to carotid narrowing.

Prediabetic obese adolescents have a more atherogenic lipoprotein profile compared with normoglycemic obese peers.

OBJECTIVE To compare lipoprotein profiles of prediabetic to normoglycemic obese adolescents. STUDY DESIGN Cross-sectional study of 95 obese, pubertal adolescents (12-17 years), who underwent oral glucose tolerance test, lipid panel, and lipoprotein subclass particle analysis (nuclear magnetic resonance spectroscopy). Univariate and linear regression analyses compared prediabetic and normoglycemic groups. RESULTS Of 95 obese adolescents enrolled in the study, 22.1% (n = 21) had prediabetes. They were similar to normoglycemic adolescents (n = 74) in age, race, body mass index, standard lipids, total low-density lipoprotein particles (LDL-P), and total high-density lipoprotein particles (HDL-P). However, prediabetics had higher concentrations of small LDL-P (714.0 ± 288.0 vs 537.7 ± 266.5 nmol/L, P = .01) and smaller LDL-P size (20.73 ± 0.41 vs 21.18 ± 0.65 nm, P = .003), than normoglycemic youth. Prediabetics had higher small HDL-P (18.5 ± 3.8 vs 16.6 ± 3.9 umol/L, P = .046), lower large HDL-P (4.49 ± 2.0 vs 6.32 ± 2.6 umol/L, P = .004), and smaller HDL-P size (8.73 ± 0.31 vs 9.01 ± 0.39 nm, P = .003). After adjusting for demographics, Tanner stage, and body mass index using multiple linear regression, all differences remained significant except for small HDL-P. After additional adjustment for Homeostasis Model Assessment-Insulin Resistance Index, only LDL-P size difference remained significant. CONCLUSION Obese prediabetic adolescents have a significantly more atherogenic lipoprotein profile compared with obese normoglycemic peers. Prediabetic adolescents may benefit from more aggressive interventions to decrease future cardiovascular risk.