Adelaide Institute for Sleep Health, Australia.
Epidemiological studies in a wide range of ethnic and cultural settings show that obstructive sleep apnea (OSA) (defined as >15 obstructive events/hour of sleep) affects about 5–10% of the population. The rising tide of obesity is almost certainly driving an increase in the prevalence of OSA in emerging economies such as India as well as in more developed countries. An increasing body of evidence over the last 15–20 years suggests that OSA is an independent risk factor for cardiovascular disease. Most of this evidence comes from population or clinic based cohort studies, although there are also a number of short-term randomised controlled trials of OSA treatment showing benefit for intermediate cardiovascular risk markers such as blood pressure, glucose metabolism and arterial vascular reactivity. Also, sudden death and acute myocardial infarction tend to occur preferentially in the nighttime amongst OSA sufferers. While this evidence points strongly to a possible causal link between OSA and cardiovascular diseases such as myocardial infarction and stroke, the international consensus is that definitive evidence for such a link is currently lacking and can only be obtained by rigorously planned and executed large-scale randomised controlled trials. Unfortunately, too often in the past, results from observational data or short term treatment studies have shown ‘compelling’ evidence in favour of a causal relationship between a putative causal factor and cardiovascular disease only to find that properly conducted randomised controlled trials targeting hard endpoints show no such effect and in some instances even harm resulting from the treatment. The Sleep Apnea cardio Vascular Endpoints (SAVE) study is an investigator designed and led multi-centre, international, randomised controlled trial of continuous positive airway pressure (CPAP) treatment plus usual care versus usual care alone in patients with co-occurring OSA and cardiovascular disease, which is designed to help fill this evidence gap. The SAVE trial will extend over 5 years and involve approximately 5000 subjects. It commenced in China and Australia in late 2008 and plans are underway to involve investigators and recruitment sites in India and New Zealand in 2009.
