Junkfood Science: Is bariatric surgery really a cure for sleep apnea?

August 24, 2008

Is bariatric surgery really a cure for sleep apnea?

Sleep apnea is one of the criteria used to support the ‘medical necessity’ of bariatric surgeries. To qualify for insurance coverage by many major insurers and the Centers for Medicare and Medicaid, and, for many years, to have surgery covered through Medicare disability, even those with moderate obesity (BMI≥35) could be a candidate if their surgeon said they had a “serious obesity-related morbidity, such as obstructive sleep apnea.”

Is bariatric surgery actually an effective treatment for obstructive sleep apnea (OSA) and can OSA even really be attributed to obesity?

A study just published in the Journal of Clinical Sleep Medicine examined the effects of bariatric surgery on the resolution of OSA, using polysomnography, also called a sleep study, the most comprehensive and detailed evaluation of physiological measures during sleep and the most accurate clinical test used to diagnose OSA and determine its severity.

According to Medscape, this study showed “Bariatric Surgery May Improve Obstructive Sleep Apnea,” while Medpage Today seemed to report the opposite, saying that “Bariatric Surgery Doesn’t Put Sleep Apnea to Rest.” Both online publications offered continuing education credits for doctors. What did the study really show?

This study was titled “Persistence of Obstructive Sleep Apnea after Surgical Weight Loss.” That provides a clue to what the authors found, but let’s take a closer look.


It might seem intuitive that fat people could ‘suffocate’ on their fat in their sleep and have obstructive sleep apnea. But, as Dr. Christopher J. Lettieri, M.D. and colleagues at Pulmonary, Critical Care and Sleep Medicine Service, Walter Reed Army Medical Center in Washington, D.C., wrote: “Obesity is neither necessary nor sufficient for the development of obstructive sleep apnea [OSA]. A corollary to this statement is that weight loss following bariatric surgery may not be sufficient to resolve OSA.”

Obesity does not cause airway obstruction. People of all sizes have it. The symptoms, according to Mayo Clinic, include: daytime sleepiness (hypersomnia); loud snoring; episodes of breathing cessation, choking or gasping during sleep; abrupt awakening with shortness of breath; awakening with a dry mouth or sore throat; and morning headaches. To clinically diagnose OSA and define its severity, though, sleep medicine doctors use the “apnea-hypoxia index” and those with mild OSA have 5-14 episodes of apnea-hypoxia an hour, while severe OSA have 30 or more apnea-hypoxic episodes per hour. Many patients with very severe disease can exceed 100 events an hour.

Even while OSA may be associated with obesity, said Dr. Lettieri and colleagues, one cannot assume that weight loss will improve OSA. This caution is especially important, given that weight loss is temporary and “many individuals who initially achieve significant weight reductions regain a portion of their weight.”

“It might be assumed that bariatric surgery resulting in significant weight loss would also improve obstructive sleep apnea,” they wrote. “However, many patients report persistent somnolence and snoring despite substantial weight loss.”

Yet, “few studies have reported outcomes in terms of frequency of disease resolution using postoperative polysomnography,” said Dr. Lettieri and colleagues. So, rather than rely on subjective, undefined reports of sleep apnea and treatment success, they conducted polysomnography evaluations. Of the 145 people evaluated at their hospital’s bariatric surgery center from January 2003 to January 2005 for bariatric surgery, 25 presented with symptoms suggestive of possible OSA and were referred to their sleep clinic prior to surgery. These 25 bariatric patients ranged in ages from 38 to 57, with average BMIs of 51, and 75% were women. All patients referred to them met the criteria for severe OSA, per the American Academy of Sleep Medicine, with about 47.9 apnea-hypoxia events per hour and were prescribed CPAP for home use.

Of these 25 bariatric patients, one died of a pulmonary embolism post-op. Each of the remaining 24 patients was re-evaluated in their sleep clinic about 1 year (328 to 677 days) after their surgeries. While the average number of apnea-hypoxia events were reduced in most patients, there was substantial variability, with two showing more events, even after dropping 18.4 kg/m2 in BMI. “The severity of OSA improved in only 50% of subjects,” they reported, but all of the patients, except for one, still had persistent OSA. All patients with OSA were observed to still snore during their follow-up polysomnography exams, they found. And “nearly half reported a persistence of daytime somnolence, and more than half continued to have Epworth Sleepiness Scale scores greater than 10.”

The researchers also attempted to examined whether bariatric surgery reduced the need for CPAP and found that 20 out of 23 of the patients with continued OSA still needed CPAP. Although the mean pressures required were reduced by 3.1 cm H20, which would predictable by their size, they still required CPAP. “Patients and healthcare practitioners should recognize that reliance on weight loss as a ‘cure’ for OSA may lead to an inappropriate cessation of CPAP therapy,” they cautioned. “Failing to recognize or treat persistent OSA may significantly impact health and quality of life.”

Popular claims don't equal sound evidence

“Despite numerous claims in the lay press that bariatric surgery can cure OSA, several studies have shown that OSA may persist following weight loss,” they noted. Even in those studies claiming to show substantial reductions in apnea-hypoxia index, “a very small minority of patients actually experienced resolution of obstructive events after sustained weight loss and many continued to require CPAP therapy,” they noted. Not only that, but “recurrence or worsening of sleep apnea has been observed following an initial weight reduction even without a concomitant weight increase.”

Interestingly, they noted that bariatric studies reporting reductions in apnea-hypoxia index with weight loss “overshadow the fact that surgical weight loss may not cure sleep disordered breathing.” Even this study, they found that “despite dramatic reductions in our patients’ apnea-hypoxic index the overall prevalence and severity of OSA remained high.”

They pointed out that in reports purporting to show a resolution of OSA after bariatric surgery, the authors didn’t describe how they defined ‘resolution’ or if polysomnography was obtained after weight loss. The study they referenced to illustrate this flaw was the Buchwald 2004 study in JAMA, which had claimed that 86.6% of gastric bypass patients and 94.6% of lap band patients had complete resolution of their symptoms.

As Dr. Lettieri and colleagues observed, “patients who felt that their snoring had resolved were at much higher risk of inappropriately discontinuing CPAP therapy” because “unfortunately, resolution of subjective snoring did not predict reductions in the [actual] severity of OSA.” They cautioned: “Patients and physicians need to recognize that subjective resolution of snoring does not equate to improvements or cure of OSA following weight loss.

Some bariatric studies have attempted to claim bariatric surgery benefits OSA by defining a ‘significant response’ as a 50% reduction in the apnea-hypoxia index and less than 15-20 events per hour, Dr. Lettieri and colleagues noted. Even applying these loose criteria, their study found only 3 or 4 patients could have been said to show improvement in their OSA with surgery. “Use of these criteria supports our concern that many, if not most, individuals will have persistent OSA despite significant weight loss following surgery,” they said.

In this study, only 20% of the bariatric patients at their institution were diagnosed with OSA, but this study was not attempting to determine the prevalence of OSA among bariatric patients. However, they believe that their findings concerning the affect of bariatric surgery on OSA among patients diagnosed with OSA, even in this small study, do accurately reflect real-world observations that are meaningful to clinicians. As they concluded:

Surgical weight loss alone frequently does not cure OSA, although it does tend to reduce the severity of disease as measured by the AHI and may lower CPAP pressures required to ablate apneic events as was found in this study... However, no long-term outcome data exist to clearly demarcate how much of a reduction in the AHI or CPAP pressures is required to result in meaningful reductions in symptoms and comorbidities related to OSA. Until the impact of surgical weight loss is better defined, patients should be counseled that [they] are likely to continue to require treatment for OSA.

Does the clinical evidence support the use of bariatric surgery as an effective intervention for obstructive sleep apnea? No.

© 2008 Sandy Szwarc

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