Sleep apnoea syndrome in 2011: current concepts and future directions

In the past two decades, obstructive sleep apnoea (OSA) has been identified as a common clinical condition. Epidemiological studies have confirmed a high prevalence of the disease in middle-aged adults. Upper airway collapse occurring during sleep in OSA is still not fully understood but new directions, such as pharyngeal neuropathy and fluid shift towards the neck, have been reported, in addition to obesity and craniofacial changes. OSA is associated with significant excessive daytime sleepiness and cognitive impairment, as well as marked cardiovascular and metabolic morbidities, leading to a significant increase in mortality. Sympathetic activation, oxidative stress and systemic inflammation have been shown to be the main intermediary mechanisms associated with sleep apnoea and intermittent hypoxia. There are now convincing data regarding the association between hypertension, arrhythmias, stroke, coronary heart disease, increased cardiovascular mortality and OSA. Data in OSA models and animal models are now available that support the link between sleep apnoea and atherosclerosis and dysmetabolism. Whether treating sleep apnoea enables chronic cardiovascular and metabolic consequences in OSA to be reversed remains to be established in adequately designed studies, particularly in comparison with usual treatment strategies. In addition, large randomised controlled trials are currently being conducted that will enable a rationale for treatment in various subsets of patients to be established, taking into account age, sex and comorbidities. Also, specific conditions, such as central sleep apnoea (CSA) associated with left ventricular failure and obesity hypoventilation syndrome, have been studied more actively in recent years with regard to pathophysiology and treatment. There is a need to pay closer clinical attention to these conditions and to set up adequate clinical trials.