RESUMO
STUDY OBJECTIVES: Current evidence in adults suggests that, independent of obesity, obstructive sleep apnea (OSA) can lead to autonomic dysfunction and impaired glucose metabolism, but these relationships are less clear in children. The purpose of this study was to investigate the associations among OSA, glucose metabolism, and daytime autonomic function in obese pediatric subjects. METHODS: Twenty-three obese boys participated in: overnight polysomnography; a frequently sampled intravenous glucose tolerance test; and recordings of spontaneous cardiorespiratory data in both the supine (baseline) and standing (sympathetic stimulus) postures. RESULTS: Baseline systolic blood pressure and reactivity of low-frequency heart rate variability to postural stress correlated with insulin resistance, increased fasting glucose, and reduced beta-cell function, but not OSA severity. Baroreflex sensitivity reactivity was reduced with sleep fragmentation, but only for subjects with low insulin sensitivity and/or low first-phase insulin response to glucose. CONCLUSIONS: These findings suggest that vascular sympathetic activity impairment is more strongly affected by metabolic dysfunction than by OSA severity, while blunted vagal autonomic function associated with sleep fragmentation in OSA is enhanced when metabolic dysfunction is also present.
Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Resistência à Insulina/fisiologia , Obesidade/complicações , Obesidade/fisiopatologia , Apneia Obstrutiva do Sono/etiologia , Apneia Obstrutiva do Sono/fisiopatologia , Adolescente , Barorreflexo/fisiologia , Glicemia/metabolismo , Pressão Sanguínea/fisiologia , Criança , Frequência Cardíaca/fisiologia , Humanos , Masculino , Modelos Neurológicos , Fatores de Risco , Nervo Vago/fisiopatologiaRESUMO
OBJECTIVE: To examine whether anthropometric measurements, blood pressure (BP), fasting total cholesterol, and low-density lipoprotein are related to ultrasound measures of carotid intima-media thickness (CIMT) in children and teenagers with no known risk factors for cardiovascular disease. STUDY DESIGN: This cross-sectional study included 599 subjects, 6 to 20 years of age (292 males, 307 females; 224 Hispanics, 210 European-Americans, 126 African-Americans, and 39 Asian-Americans) whose body mass index, waist circumference, BP, lipid profiles, and values for CIMT were determined. RESULTS: Measures of CIMT were significantly greater in males than females (P=.006) and in African-Americans when compared with other ethnic groups (all P < .05). There were no relations between age, diastolic BP, or fasting levels of triglycerides, total cholesterol, or low-density lipoprotein values and CIMT measures, regardless of sex or ethnic background. Stratified multiple regression analysis indicated that body mass index and waist circumference independently predicted CIMT in both males and females, even after controlling for age, weight, BP, fasting lipid levels, and ethnic background. CONCLUSION: Increased body mass and adiposity are associated with increased intima-media thickness in children and teenagers. This association is present in children not considered overweight, underscoring the need for the continued promotion of adequate nutritional and physical exercise behavior during childhood.