Aug 082012

Obstructive sleep apnea (OSA) might be the perfect disease to describe the American health care system. The condition is overwhelmingly due to our over-indulgence and under-activity; its expensive diagnosis (polysomnography) and best treatment (CPAP) help physicians and device manufacturers prosper while consternating those who pay (the government and insurance companies), who then threaten to cut off the money-spigot and end the CPAP and PSG payment party. The sleep doctors counter with papers that argue they're indispensable to American health, that CPAP cures metabolic syndrome, that CPAP may save lives.

Thanks to Jane Colish, Jonathan Walker, Davinder Jassal et al, sleep specialists can now also add the slogan "CPAP is good for your heart" to their message, for counseling both portly patients and parsimonious policymakers. The authors report their results in the March 2012 Chest.

What They Did

Colish et al prospectively studied 47 patients from two academic medical centers between 2007 and 2010. All had a new diagnosis of obstructive sleep apnea, mostly severe (mean AHI 63), had never used continuous positive airway pressure (CPAP), and had no prior history of cardiovascular disease. For one year at 3 month intervals, investigators performed transthoracic echocardiography (TTE) and collected cardiac labs including C-reactive protein (CRP), N-terminal pro-B-type natriuretic peptide (NT-pro BNP), and troponin T (TnT), as well as cardiac MRI.

What They Found

All patients were adherent with CPAP treatment, and on average they experienced detectable, favorable remodeling of their heart muscles. Specifically, they had a reduction in their right ventricular end-diastolic diameter, peak RV systolic pressure, right atrial volume index, and left atrial volume index. These improvements were seen at 3 months, and improvement was still greater at 1 year. Cardiac markers did not change from baseline after CPAP therapy.

What It Means

There's no reason to doubt that by relieving hundreds of thousands of episodes of airway obstruction, CPAP therapy could reduce strain on the heart and encourage favorable cardiac remodeling. There's enough evidence in favor of cardiovascular benefits of CPAP therapy that randomizing patients with OSA to sham therapy would be unethical, in the U.S. today. That leaves us with pathophysiologic studies like this one, and past and future observational studies comparing compliant vs. non-compliant patients; these studies' baked-in selection bias and OSA patients' multiple cardiovascular risk factors mean the question of whether CPAP saves lives might never be answered definitively.

Meanwhile, rising obesity rates mean tens of millions of people have or soon will have undiagnosed OSA, representing a potential cost of tens of billions of dollars to diagnose and treat them all under the current scheme. The U.S. government and insurance companies are responding by plotting to target high-billing sleep doctors to change behavior within the specialty, and payment reductions are sure to follow. Home testing for OSA would reduce cost-per-test, but could result in huge increases in the numbers tested and thus total costs, if primary care physicians can send patients home with a simple kit.

As for the real solution to this, it's always been around our waists. Maybe the U.S. Dept. of Health and Human Services (who oversee Medicare) could talk to the U.S Dept. of Agriculture (whose industry-backed legislator overseers protect the corn subsidies that perpetuate the obesity epidemic)...but that's only if you want to really get Big-Picture about it.

Colish J et al. Obstructive Sleep Apnea: Effects of Continuous Positive Airway Pressure on Cardiac Remodeling as Assessed by Cardiac Biomarkers, Echocardiography, and Cardiac MRI. Chest; 2012;141 (March):674-681.

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CPAP gives the heart a tune-up for 1 year or 30 million beats, whichever comes first