Sleep-disordered breathing and cardiovascular disease.

Sleep-disordered breathing (SDB) describes a group of disorders characterised by abnormalities in the frequency and/or depth of breathing while asleep. The most common type is the obstructive sleep apnoea/hypopnoea syndrome (OSAHS); it affects 2-4% of the adult population and is an independent risk factor for hypertension. Another type is central sleep apnoea (CSA), which includes Cheyne-Stokes respiration; it is most commonly seen in patients with congestive heart failure and other critical illnesses including cerebrovascular accidents. There is accumulating evidence that both these types of SDB are associated with cardiac failure, arrhythmias and coronary artery disease. Treatment of OSAHS with continuous positive airway pressure (CPAP) has lowered blood pressure, reduced the frequency and severity of some arrhythmias, and improved markers of endovascular inflammation. CPAP has had a mild positive effect on left ventricular function in chronic heart failure by treating co-existent SDB, but it has not improved mortality, possibly because it does not fully treat associated CSA. Clinicians need to be aware of the increasing associations of SDB, especially OSAHS, with cardiovascular dysfunction, as treatment of co-existent SDB will not only improve sleepiness, quality of life, and driving risk, but there is growing evidence that it may also improve cardiovascular risk itself, even in non-sleepy subjects.