Sleep apnea, autonomic dysfunction, and vascular diseases

Habitual snoring and obstructive sleep apnea syndrome (OSAS) are common respiratory disorders affecting up to 10% of the population. Obstructive sleep apnea syndrome is characterized by recurrent episodes of complete or partial interruption of ventilation during sleep, caused by collapse of the upper airways. Compared with the general population, the prevalence of OSAS is higher among patients with cardio- and cerebrovascular conditions. About 50% of OSA patients are hypertensive and about 30% of hypertensive patients also have obstructive sleep apneas (OSAs). Epidemiological data indicate that OSA is involved in the development or progression of cardio- and cerebrovascular diseases. Obstructive sleep apnea has been recognized as a risk factor for the onset of arterial hypertension, coronary artery disease, heart failure, and stroke, independent of confounding covariates (i.e., age, gender, smoking, alcohol, obesity, diabetes, or dyslipidemia). The underlying mechanisms explaining the association between OSA and cardio- and cerebrovascular diseases have not been fully defined. Sympathetic overactivity appears to be the critical link between OSA and the pathogenesis of hypertension, as documented by clinical studies and strong experimental evidence from animal studies. Several intermediate mechanisms, including oxidative stress, disorders in coagulation factors, endothelial dysfunction, platelet activation, and increased inflammatory processes have also been implicated in the pathogenesis of cardio- and cerebrovascular diseases.