Sleep disorders and heart disease: Complicated relationship needs more research.
Cardiology Today, February 2016
In recent years, strong evidence has emerged linking sleep disorders to various forms of heart disease — in particular, HF and hypertension. What is less certain, however, is whether treatment of sleep disorders before the onset of heart disease can prevent heart disease, and how to incorporate evaluation of sleep disorders such as sleep apnea into a cardiologist’s general clinical practice.
“Untreated, sleep apnea is associated with increased CHD events, such as MI, atrial fibrillation and other arrhythmias, stroke, sudden death and progression to HF,” Rami Khayat, MD, associate professor of medicine at Ohio State University and director of its Sleep Heart Program, toldCardiology Today.
Although evidence continues to accumulate on the mechanisms of sleep apnea and its association with different forms of heart disease, there is still much uncertainty about how the two relate to each other and the optimal treatments for patients with both.
“It is difficult to tease out whether it is the CVD or the obesity or the diabetes that causes obstructive sleep apnea, or whether obstructive sleep apnea is there as a bystander,” Martin R. Cowie, MD, MSc, FRCP, FRCP (Ed), FESC, professor of cardiology at Imperial College London and Royal Brompton Hospital, said in an interview. “But if clinicians and cardiologists screen for sleep-disordered breathing, they will find a substantial number of people that have this disorder.”
Further complicating the issue were the unexpected results of the SERVE-HF study presented at the 2015 European Society of Cardiology Congress and published in The New England Journal of Medicine. Cowie and fellow investigators for the SERVE-HF study found that treating central sleep apnea (CSA) with adaptive servo-ventilation in patients with HF led to worse outcomes.
Wide prevalence of sleep apnea
The most common form of sleep apnea, obstructive sleep apnea (OSA), is widely prevalent in people with a variety of heart diseases.
It is estimated that “40% of patients with OSA have hypertension, and about 40% of patients with hypertension will have OSA,” Virend K. Somers, MBChB, DPhil, FAHA, FACC, the Alice Sheets Marriott Professor of Cardiovascular Diseases at Mayo Clinic, told Cardiology Today. However, he noted that “these numbers depend on demographics.” For example, “if you have more women [in a specific demographic], there might be a lower likelihood of OSA, and if you are not obese, you’ll have less sleep apnea. For AF, if you take all the patients with AF coming for cardioversion, 50% will have a high likelihood of significant sleep apnea. If we look at people who come into the hospital with MI, the level of sleep apnea tends to be around 50% to 60%. That has been consistent across different studies in different environments.”
Much of the research on the link between heart disease and sleep apnea has been conducted in patients with HF. It is estimated that between 50% and 70% of patients with HF have some form of sleep apnea. “In the U.S. population, if you [look at] patients with HF, you’d find about 35% will have OSA and maybe 30% will have CSA,” Somers said.
Ajay V. Srivastava, MD, FACC, advanced HF cardiologist at Scripps Clinic, La Jolla, California, said patients with HF or hypertension are more likely to have sleep apnea based on an increasing number of the following characteristics: significant snoring, fatigue during the day, history of high BP, partner noticing that they stop breathing at night, BMI greater than 35 kg/m2, neck circumference greater than 14 inches and male sex.
Various studies have reported that, compared with age-, sex- and BMI-matched controls, those with OSA may have a twofold risk for onset of HF, threefold risk for onset of stroke and fourfold risk for onset of hypertension, experts told Cardiology Today.
CSA is a condition found almost exclusively in patients with HF and “people who take a lot of opiates for good or bad reasons,” Cowie said. Unlike OSA, which often arises before the onset of HF, hypertension or other heart disease, CSA typically arises after the onset of HF, which means that the relationship between OSA and heart disease may be quite different than the one between CSA and heart disease.
