[Metabolic consequences of untreated obstructive sleep apnea syndrome]

There is a recognized association between obstructive sleep apnea syndrome and metabolic syndrome, designated syndrome Z. The criteria for metabolic syndrome include at least three of the following factors: central obesity (waist circumference ≥ 102 cm for males and ≥ 88 cm for females); triglycerides ≥ 150 mg/dL; HDL cholesterol < 40 mg/dL for males and < 50 mg/dL for females; arterial blood pressure ≥ 130/85 mmHg; and fasting glucose ≥ 100 mg/dL. Central obesity is associated with OSAS and metabolic syndrome, and there is evidence that obstructive sleep apnea is an independent risk factor for obesity, glucose intolerance and insulin resistance. The implied mechanisms result from the activation of the sympathetic nervous system and of the hypothalamus-hypophysis-adrenal axis; activation of pro-inflammatory markers, such as IL-6 and TNF-α; and the reduction in adiponectin levels, principally triggered by intermittent hypoxemia related to apnea. Despite such evidence, the results are controversial regarding the benefits of treating sleep apnea with CPAP in the presence of these metabolic alterations. In addition, the few studies that have addressed sleep apnea as a risk factor for dyslipidemia have presented conflicting results. Population-based, longitudinal controlled studies are necessary in order to elucidate the interaction between sleep apnea and metabolic consequences so that these individuals are properly treated.