Sleep has always been associated with the overall concept of health. Over the past decades, the association between sleep and cardiovascular diseases has been emerging. Several sleep disorders are now known to be associated with cardiovascular disease. One of the most notorious associations is with obstructive sleep apnea (OSA). OSA has been linked to a higher incidence of hypertension, with up to 50% of patients with OSA having an elevated blood pressure. Continuous Positive Airway Pressure (CPAP) treatment has been shown to improve blood pressure. The pathogenesis of hypertension in OSA is related to the sympathetic nervous system activation (SNA) that occurs following each apneic episode and that requires the presence of intermittent hypoxia. OSA is similarly linked to an increased risk of cardiac ischemia as well as congestive heart failure.
Treatment with CPAP can improve cardiovascular mortality and left ventricular ejection fraction. OSA is also associated with arrhythmias and strokes. Central sleep apnea and Cheyne Stokes respiration have been described in patients with congestive heart failure and their presence could lead to a worse prognosis. CPAP treatment improves ejection fraction but the effect on mortality has not been proven. Other sleep disorders are linked to increased cardiovascular risk. These include insomnia, short and long sleep duration, circadian rhythm disorders and possibly restless leg syndrome. Sympathetic activation in the form of elevated norepinephrine levels has been documented in patients with OSA. Other markers studied include inflammatory markers and markers of oxidative stress. Although a lot of progress has been made, a specific molecular signature for OSA is yet to be found.
