Can Bariatric Surgery Really Resolve My Sleep Apnea?March 22, 2017
Obstructive Sleep Apnea (OSA) is an extremely common public health problem present in 2% to 4% of the general population. It has been linked to the development of hypertension and is a risk factor for the incidental development of stroke, coronary artery disease, congestive heart failure, and atrial fibrillation (a common irregular heart rhythm).
Obesity & Sleep Apnea
About 70% of people with OSA are obese. Conversely, the prevalence of the disorder among obese people is approximately 40%. In morbidly obese patients (BMI≥45 kg/m2 ), the prevalence of OSA ranges from 50% to 77% and in those with BMI of 60 or more, the disorder occurs in 90%. For every 20lb increment in weight, the risk for OSA increases by more than two-fold while an increase in the body mass index by one standard deviation is associated with a four-fold increase in the prevalence of OSA. It is accepted that central obesity exacerbates OSA because of fat deposits in the upper airway.
Research confirms that OSA is more common in men than women. Obesity can lead to critical narrowing of the upper airway. Excess body weight affects the mechanics of the airway. Fat deposits have a negative impact on the neural control of respiratory muscles. Genetic factors may affect fat distribution.
The increased fat deposits in the upper airway (pharyngeal and the submental regions) cause soft tissue enlargement and contribute to a critical narrowing of the airways. Airway swelling (mucosal edema secondary to vibration trauma related to snoring, vascular congestion, and the inflammatory status related with obesity per se) contribute to anatomical narrowing.
Diagnosing Sleep Apnea
Screening and treating OSA should be an integral part of the preoperative and postoperative care of the bariatric surgical patient because of the high prevalence of OSA in bariatric patients and the consequences of undiagnosed and untreated OSA in the postoperative period (respiratory complications).
Polysomnography at an accredited sleep center is appropriate to identify treatable comorbid sleep disorders for obese patients presenting with sleep disturbances. Weight loss in those who are obese reduces the severity of OSA regardless of the method used, although surgical procedures may produce more objective results.
The two main reasons to detect and treat OSA are to improve symptoms and to decrease cardiovascular risks. Data shows that treatment of OSA improves symptoms and quality of life.
There are two common ways to diagnose obstructive sleep apnea, in lab testing known as a Polysomnography or PSG (gold standard) and Home Testing known as HSAT.
OSA severity is rated by the sleep study AHI, the hourly rate of apneas (cessations in breathing) and hypopneas (upper airway blockages or obstructions) averaged over the total sleep time, or, in the case of HSAT, by the REI. An AHI of 4 per hour or less is considered normal. Mild OSA is diagnosed with an AHI of 5 to 14 per hour, moderate OSA with AHI of 15 to 29 per hour, and severe OSA with AHI being 30 per hour or higher. In most laboratories, correlation of the AHI with specific sleep stages and body positions is usually performed to determine whether positional therapy may be offered, as many patients have OSA only during the supine sleep position (position-dependent OSA), and some manifest OSA only during REM sleep in the supine position.
Mild OSA is diagnosed with an AHI of 5 to 14 per hour, moderate OSA with AHI of 15 to 29 per hour, and severe OSA with AHI being 30 per hour or higher. In most laboratories, correlation of the AHI with specific sleep stages and body positions is usually performed to determine whether positional therapy may be offered, as many patients have OSA only during the supine sleep position (position-dependent OSA), and some manifest OSA only during REM sleep in the supine position.
Treating Sleep Apnea
Therapeutic options for snoring and sleep apnea include reducing nasal congestion or obstruction, positional therapy, nasal continuous positive airway pressure (CPAP/BPAP), oral appliances, the nasal expiratory positive airway pressure device, oral pressure therapy (OPT), or surgical management. CPAP/BPAP remains the most effective therapy for OSA. The other options are viable in specific circumstances.
The Impact of Weight Loss on Sleep Apnea
Weight loss may reduce soft tissue in the neck, making the oropharynx less compressible. The improvement in lung volumes accompanied by weight loss also favor enhancement of longitudinal traction on the upper airway, the so-called “tracheal tug.” Careful follow-up is needed because remissions in certain patients may not be permanent. Alcohol and other substances that reduce the upper airway tone, cause sedation or reduced responsiveness worsen OSA and should be prudently avoided.
The most important therapy for OSA in obese patients is weight loss. Weight loss changes pharyngeal anatomy and decreases airway collapsibility by increasing the pharyngeal closing pressure. One study reported a significant reduction in the lateral subcutaneous neck fat with only a 10% weight loss.
Several other small studies have reported a significant association between the extent of weight loss and reduction in the severity of OSA. Even a modest weight reduction can lead to amelioration of SDB in certain patients. However, the magnitude of weight reduction that can improve sleep apnea varies across patients. Patients with severe obstructive sleep apnea experiencing larger reductions in the AHI than those with a moderate disease at baseline.
The most impressive results of AHI improvement are derived from those morbidly obese patients who underwent bariatric surgery. A recent meta-analysis of surgical weight loss on measures of OSA showed a decrease of 38.3 events/h corresponding to 71% reduction in AHI.
It is important to align patient expectations with realistic outcomes, practitioners counseling patients on the risks and benefits of bariatric surgery should communicate that OSA may or may not be cured by post-surgical weight loss.
In particular, concern for residual OSA should remain high in patients with other independent risk factors of OSA, such as male sex, older age, severe OSA at baseline, or residual obesity.
About 30% to 40% of patients who are able to achieve substantial weight loss may become cured of their OSA. Residual disease is seen in about 62% after bariatric surgery with a mean residual AHI of more than 15 events per hour. A disease severity of 15 events per hour reflects moderate disease. Pooling data from large meta-analyses shows that about 25% of patients achieve an AHI < 5 (cure).
Postoperative monitoring of sleep quality and utilization of CPAP/BiPAP as weight loss progresses is recommended. Many patients prematurely discontinue the use of CPAP/BiPAP within the first three months after bariatric surgery because of dramatic symptomatic improvement and sometimes because of intolerance to “high” pressure settings. Therefore, we recommend a formal postoperative consultation for reevaluation of the condition and reduction in CPAP/BPAP settings if required. Information acquired from the CPAP/BPAP device (especially if auto-adjusting i.e. providing information about the amount of air pressure required by the patient) often proves useful in clinical decision making.
ABOUT THE AUTHORRandip Singh, MD, joined Overlake Internal Medicine Associates in 2006. Born in Maryland, he received his medical degree from Dayanand Medical College in Punjab, India, and completed his internship in Internal Medicine at Atlantic City Medical Center. Dr. Singh also completed a Neurology Residency and Chief Residency at Georgetown University, Washington DC. Dr. Singh is board certified in Neurology and Sleep Medicine. He is currently a Clinical Instructor in Neurology at the University of Washington.