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Focus on sleep apnea and cardiovascular events: SAVE Study

A pivotal research program linking sleep and cardiovascular medicine experts across the Asia-Pacific region is taking shape. The study aims to produce high level evidence that will shape clinical decision making and future health policy in an area of significant global health burden.

What is Obstructive Sleep Apnea?

Obstructive Sleep Apnea (OSA) is a common condition characterised by repeated episodes of obstruction (apnea) or narrowing (hypopnea) of the upper airway during sleep. Other symptoms include loud snoring and daytime sleepiness. It is estimated that 4-10% of middle-aged men and women suffer from OSA, defined as more than 15 obstructive events during each hour of sleep. Men are more likely than women to suffer from OSA and other risk factors include ageing and obesity. The condition leads to fatigue and poor concentration, and places people at increased risks of accidents. There is increasing evidence that OSA may also contribute to the development of cardiovascular disease such as hypertension, stroke, coronary artery disease, heart failure and sudden death. However, most cases of OSA go undetected, and therefore untreated.

How do you treat OSA?

Treatment using Continuous Positive Airway Pressure (CPAP) reduces symptoms and improves quality of life for OSA patients. Delivered through a mask worn by patients while they sleep, CPAP is generally well-tolerated and improves sleep and subsequently, their alertness during the day.

However, researchers at The George Institute’s Neurological and Mental Health Division in collaboration with The Adelaide Institute for Sleep Health believe there is enough evidence to suggest the use of CPAP can also improve cardiovascular risk factors to warrant further investigation. SAVE researcher, Dr Emma Heeley, feels OSA is an ideal focus considering its prevalence and the availability of cost-effective treatment. Emma acknowledges "we could make a major advancement in health care, if it can be established that Obstructive Sleep Apnea is a significant cause of cardiovascular events, including premature death and disability."

Researchers anticipate that screening for OSA could become part of routine clinical care in cardiovascular medicine, and integrated within future public health campaigns aimed at reducing cardiovascular morbidity and mortality.

OSA in the Chinese setting

Dr Heeley explains, "There is little community awareness of OSA in China compared to developed countries. Additionally, access to treatment is severely restricted by cost - CPAP is currently beyond the means of nearly all sufferers of OSA. Thus the vast majority of cases in China currently go undetected and untreated."

Researchers at The George Institute in collaboration with Australian sleep and cardiovascular medicine experts have designed the SAVE (Sleep Apnea cardioVascular Endpoints) Study, with a focus on China. The study will be conducted in three separate phases.

The SAVE Study Status

1. The SAVE Validation Study has involved the recruitment of approximately 150 subjects with high cardiovascular risk from the the Luwan District in Shanghai with the aim of establishing the frequency of OSA, and testing the usefulness of a simple home, overnight breathing testing device for the diagnosis of condition. The study involves comparing a simple test of nasal air flow and oxygen levels in the blood (oxymetry) against a more sophisticated diagnostic test for OSA , called polysomnography, which records various physiological variables such as brain electrical activity, breathing and heart rate while subjects are asleep. The aim is to determine whether the simple device would be useful to rapidly include subjects into the later phases of SAVE.
2. The SAVE I study, is a randomised controlled trial of CPAP therapy against usual care in 600 people with co-existing high cardiovascular risk and moderate to severe OSA. Subjects will be recruited from several dozen sites in China, India and Australia with the aim of determining the effects of the treatment on blood pressure and other markers of cardiovascular disease. The study will also establish the feasibility and logistical issues in proceeding to the main phase of the study, SAVE II.
3. The SAVE II Trial, or the main study, will begin early 2009. The aim of this study is to determine the effectiveness of CPAP in reducing the incidence of cardiovascular disease, including strokes, heart attacks, heart failure and death in 5000 subjects recruited from over 100 centres, primarily in the Asia-Pacific region.

Partners

Respironics Inc has provided substantial seed funding and equipment for SAVE I. ResMed Australia have also provided significant equipment for the study. Industry organisations and other interested parties who would like to become partners in SAVE are encouraged to contact the Principal Investigator of the study, Professor Doug McEvoy of the Adelaide Institute for Sleep Health at Flinders University on +61 (0)8 8275 1952; email doug.mcevoy@rgh.sa.gov.au or by writing to:

The Adelaide Institute for Sleep Health
Repatriation General Hospital
Daws Road
Daw Park
South Australia 5041