This first randomized clinical trial in the world shows that patients who have obstructive sleep apnea and heart failure and who are treated for their sleep apnea can gain remarkable improvements in their heart function beyond that due to drug therapy

Toronto (March 26, 2003) - Heart function can be significantly improved in patients with congestive heart failure and obstructive sleep apnea by treating this sleep disorder with a simple easy-to-use, portable device, according to a first-ever randomized clinical trial of patients with heart failure conducted at Toronto General Hospital (TGH), University Health Network (UHN), Mount Sinai Hospital and the Toronto Rehabilitation Institute.

It is estimated that about one third of all patients with heart failure have obstructive sleep apnea.

The study tested 24 patients with heart failure who also had obstructive sleep apnea. All patients were on medication for their heart failure. Twelve (12) participants were then randomly assigned to receive medical therapy alone (medication), and another 12 were randomly assigned to receive treatment (medication) for their heart failure, as well as treatment for their obstructive sleep apnea using a device called continuous positive airway pressure (CPAP). Patients were tested before and after one month of either receiving medication alone or both the CPAP treatment and medication.

Obstructive sleep apnea is a disorder in which involuntary breath holding during sleep occurs at least 15 to 20 times an hour at night. This happens when the muscles holding the throat open relax during sleep, narrowing and obstructing the throat. This then prevents the flow of air into the lungs, causing suffocation and stress to the failing heart. The commonest risk factor for obstructive sleep apnea is obesity.

CPAP, which is used to treat sleep apnea, consists of a small mask that is placed over the nose during sleep and is connected by tubing to an air pressure pump that is plugged into a wall socket. Air pressure in the tubing is transmitted to the mask and then flows continuously through the nose into the throat, propping it open and preventing it from collapsing during the night. This eliminates obstructive sleep apnea.

Congestive heart failure is a disease of the heart muscle which has left it so weak that it cannot pump sufficient blood to meet the demands of the rest of the body for blood and oxygen. The commonest cause of heart failure is a heart attack. About 1% of the adult population in North America has congestive heart failure, and it is the leading cause of hospital admission for individuals above the age of 65.

The results of this study are published in a paper entitled: "Cardiovascular Effects of Continuous Positive Airway Pressure in Patients with Heart Failure and Obstructive Sleep Apnea", in the March 27th issue of the The New England Journal of Medicine.


  • Sleep Apnea Episodes Decrease: In the patients receiving medication only, there was no change in the frequency of their obstructive sleep apnea episodes which remained at 45 episodes per hour. In contrast, among the patients receiving the CPAP treatment in addition to medication, the episodes were reduced from 37 per hour to 8 per hour – an 80% reduction within one month.
  • Heart Function Improves: As a measure of heart function, the left ventricular ejection fraction was assessed as a percentage of the blood that is ejected from the heart with each contraction. In a normal heart it is about 60%. All 24 patients had left ventricular ejection fractions of less than 45%. After one month, the patients on medication alone experienced no change in their heart function. In contrast, those who were treated with CPAP had a 9 % increase in their left ventricular ejection fractions, from 25% to 34%. This means that with each beat, their hearts pumped 35% more blood than prior to CPAP therapy.
  • Heart Size Deceases: In heart failure, the heart enlarges, which increases its workload and makes it less efficient in pumping blood. The group receiving medication only did not have any change in heart size. However, after one month of treatment with CPAP, the average dimension of the heart at the end of a beat was reduced by three (3) millimetres from 55 to 52 millimetres.
  • Blood Pressure Decreases: The blood pressure of the patients receiving medication only did not change at the end of one month. In contrast, the blood pressure of those patients who received the CPAP treatment decreased from 126/62 to 116/59 millimetres of mercury. This 10 millimetre of mercury drop in systolic blood pressure is significant and was achieved in addition to the effects of any medication the patients were taking. Such a drop in blood pressure lessens the risk of heart attacks and stroke.
  • Heart Rate Decreases: In the group of patients who did not receive CPAP, the heart rate remained the same after one month. In contrast, among patients treated with CPAP, heart rate decreased from 68 to 64 beats per minute. This means that the CPAP-treated patients were able to achieve a higher output from the heart at a lower heart rate and blood pressure, i.e. by expending less energy.

"Prior to this study, it not been considered that heart failure might be adversely affected by something that goes on during sleep", said Dr. Douglas Bradley, lead investigator of the study, and Head of the Sleep Research Laboratories at Toronto General Hospital, Mount Sinai and Toronto Rehabilitation Institute, and Director of the University of Toronto Centre for Sleep Medicine and Circadian Biology. "We've demonstrated that obstructive sleep apnea is a previously unrecognized contributor to heart failure, and that a simple and specific therapy targeting sleep apnea can improve heart failure."

"Physicians in the community need to be aware that many patients with heart failure have obstructive sleep apnea, and that, in general, it is not being recognized or treated. We could be keeping people out of the hospital, and improving their quality of life with this inexpensive and easy-to-use effective therapy, while at the same time saving the system a lot of money," said Dr. Bradley. Key factors in diagnosing sleep apnea include: being male and obese; loud snoring and restless sleep; as well as sleepiness and fatigue during the day.

Dr. John Floras, Director of Research for the UHN Division of Cardiology, and a cardiologist at Mount Sinai Hospital was a co-investigator in the study. He adds that, "After studying the effects of obstructive sleep apnea for a decade, we are astonished at how many stresses the failing heart faces during sleep. Sleep should be a calm and restorative time for the heart and circulation, but in those patients with sleep apnea, it is not. It's as if the heart is involved in running a marathon during the night."

"In addition to physicians, it's important that patients and their families know about the signs and symptoms of sleep apnea and the tremendous benefits of therapy," says Dr. Paul Oh, Medical Director, Cardiac Rehabilitation and Secondary Prevention Program, Toronto Rehabilitation Institute. "We'll be spreading the word through our program, which is all about helping patients with heart failure and other cardiac conditions live longer and better lives."

Noel Bates, 62, of Creemore, ON, was diagnosed with heart failure in 2000. He took part in this clinical trial and agrees that treating his obstructive sleep apnea with CPAP has made a major difference in his heart function. "It's turned my life around. Three years ago, my heart failure was so severe, I was thinking and making decisions about a heart transplant. Now, my heart function has improved so much that I can go skiing and snow shoeing several times in one day. I feel like a million bucks."


This study highlights the need for physicians to be aware that treating sleep apnea in patients with heart failure can improve their heart function. Sleep apnea is often left undetected and untreated, even though CPAP treatment is a simple portable device that is partially paid for by the government in Ontario.

Screening patients with heart failure for sleep apnea should increase as a result of this study. This could help many more patients improve their heart function simply, effectively and at home.

In this study, the patients used the CPAP treatment only at night, while the measurements of heart function were taken during the day. This implies that the treatment is having beneficial carry-over effects which last throughout the day.

The study was supported by a Canadian Institutes of Health Research grant. Dr. Bradley was also supported by a Senior Scientist Award from the Canadian Institutes of Health Research, and Dr. Floras was supported by a Career Investigator Award from the Heart and Stroke Foundation of Ontario.

About Mount Sinai Hospital

Mount Sinai Hospital is recognized nationally and internationally for its excellence in the provision of compassionate patient care, teaching and research. Its key priority programs are Women's and Infants'Health, Surgical Subspecialties and Oncology, Internal Medicine and Subspecialties, and the Samuel Lunenfeld Research Institute. It is a University of Toronto-affiliated patient care, teaching and research centre.

About Toronto Rehabilitation Institute

The Toronto Rehabilitation Institute is Canada's largest hospital that provides adult rehabilitation services and complex continuing care. As a fully affiliated teaching and research hospital of the University of Toronto, Toronto Rehab also is advancing rehabilitation science.

About Toronto General Hospital

Toronto General Hospital is a partner in University Health Network, along with Toronto Western and Princess Margaret Hospitals. The scope of research and complexity of cases at Toronto General Hospital has made it a national and international source for discovery, education and patient care. It has one of the largest hospital-based research programs in Canada, with major research projects in cardiology, transplantation, surgical innovation, infectious diseases, and genomic medicine. Toronto General Hospital is a teaching hospital affiliated with the University of Toronto.

Media Contact

Phone: 416 340 4636

Back to Top