WAVES (West Australian cardioVascular Events in obstructive Sleep apnoea)

The aim of this study is to explore the interaction between obstructive sleep apnoea (OSA) and other known cardiovascular disease (CVD) risk factors (e.g., diabetes) in the pathogenesis of CVD. The study will utilise baseline data on a previously well characterised cohort of patients attending the SCGH sleep service between 2005 and 2010 – the Western Australian Sleep Health Study (WASHS). WASHS patients have previously provided clinical data (questionnaires and basic anthropometric information, eg body mass index) and blood samples (DNA and biochemical data including common measures of cardiovascular risk such as serum cholesterol) and laboratory sleep study data (full overnight polysomnography or PSG). The follow-up assessments included in WAVES will include a repeat questionnaire in all participants. The primary outcome will be incident cardiovascular disease (such as myocardial infarction). We plan to study 500 who have not developed CVD in more detail, to determine the presence of early markers of cardiovascular disease (such as left ventricular hypertrophy on echocardiogram). We will select and invite 500 according to baseline matching factors (e.g., age, gender) that predict CVD. We will perform a matched comparison in these 500; comparing those on OSA treatment with CPAP to those that did not take up treatment (i.e., 250 in each group). This subset of 500 will be asked to have the following additional assessments: sleep study, anthropometric measurements, blood pressure, ECG (electrocardiogram), an echocardiogram, 24 hour blood pressure monitor, CT scan for coronary calcium, and a dual energy xray absorptiometry (DEXA) scan. This study aims to determine whether OSA predisposes to the development of CVD, or early markers of CVD (n=500), independently of other known CVD risk factors. We will examine how OSA interacts with known CVD risk factors and determine what PSG metric of OSA severity best predicts CVD risk. We will also be able to determine the effect of standard OSA treatment i.e., CPAP on CVD risk. The majority of participants will only complete an online questionnaire which will take approximately 30mins with no visits required and no further testing. Those on CPAP therapy will have a simple appointment which will require a single 1 hour visit to the sleep clinic and 1 week of wearing a activity tracking device which can then be returned by mail. Those 500 (250 on CPAP and 250 not on CPAP) chosen for further testing will require one overnight appointment (11 hrs) and additional appointments to complete the consent and testing procedure. Total of approximately 18hrs required with no further follow up.