Sleep Disturbances/Sleep Apnea

Obstructive sleep apnea syndrome (OSAS), combining nighttime occurring intermittent obstruction of upper airways with daytime somnolence, is associated with impairment in important mechanisms of cardiovascular regulation, in particular with neural and reflex mechanisms involved in blood pressure (BP) control. The resultant sympathetic activation and the associated metabolic and humoral responses lead to important autonomic and hemodynamic changes (vasoconstriction, fluid retention, elevated blood pressure and blood pressure variability, elevated heart rate, and reduced heart rate variability), which are not only present during the apneic episodes occurring at night but also during daytime wakefulness. The presence of all these conditions, the magnitude of which is directly associated to the severity of OSAS, not only promotes future development of hypertension but also makes hypertension occurring in OSAS more severe and resistant to antihypertensive treatment and associated with profound alterations in day-to-night BP changes. The evidence mentioned above highlights the relevance of OSAS as a risk condition not only for arterial hypertension but also for other cardiovascular diseases. This chapter is aimed at reviewing: 1. The effects of OSAS on different mechanisms involved in integrated cardiovascular modulation (2) The resultant autonomic and hemodynamic responses to these alterations 2. The epidemiological evidence supporting the association of elevated BP with OSAS 3. The prognostic significance of OSAS-related hypertension 4. The diagnostic approach to OSAS-related hypertension 5. Finally, the role of pharmacological and non-pharmacological strategies on OSAS-related hypertension with emphasis on CPAP (i.e., which is known to be effective in reducing the sympathetic nervous system overdrive; a major contributing mechanism for OSAS-related alterations in BP regulation) and whether it may promote achievement of BP control and stabilization of BP levels for improving cardiovascular morbidity and mortality in OSAS patients