Hypoglossal nerve stimulation (HGNS) treatment for obstructive sleep apnoea (OSA) drops significantly as a patient's weight rises above a healthy range, according to researchers from Washington University School of Medicine in St Louis.
"Our study shows that the more overweight you are, the less likely it is that nerve-stimulation treatment will be effective in treating your sleep apnoea," said senior author, Dr Eric C Landsness, an assistant professor of neurology. "I'm not saying that we shouldn't put this device in patients with a BMI of 38 or 40. But my job as a physician is to help overweight patients make an informed decision, to better understand their odds of success and realise that the chances of it working for them may be a lot less."
The first hypoglossal nerve-stimulation device (brand name Inspire) was approved by the FDA in 2014 for use in patients with BMIs less than 25 whose moderate to severe sleep apnoea has failed treatment with other, more established therapies. Since then, eligibility requirements have loosened, with the FDA now allowing the device to be used in patients with BMIs as high as 40 and Medicare providing coverage for patients with BMIs up to 35.
HGNS was originally approved only for people with body mass indexes (BMIs) in the healthy range recently was extended to patients with BMIs up to 40, a weight range generally described as severely obese. A healthy BMI ranges from 18.5 to 24.9. The expanded eligibility criteria for the treatment provide more sleep apnoea patients with access to the increasingly popular therapy.
The study investigated whether HGNS therapy was effective for patients with OSA, whether HGNS can treat supine OSA and whether there are associations between BMI and treatment response. The findings are based on a retrospective analysis of treatment success in 76 sleep apnoea patients with BMIs of less than 35. Treatment response was defined as 50% reduction or greater in preimplantation Apnea-Hypopnea Index (AHI) score and post-implantation AHI of less than 15 events per hour.
Of 76 included patients, 57 (75%) were male, and the median (IQR) age was 61 (51-68) years. A total of 59 patients (78%) achieved a treatment response. The researchers reported that there was a clinically meaningful reduction in median (IQR) AHI, from 29.3 (23.1-42.8) events per hour pre-implantation to 5.3 (2.6-12.3) events per hour post-implantation (Hodges-Lehman difference of 23.0; 95% CI, 22.6-23.4).
In adjusted analyses, patients with BMI of 32 to 35 had 75% lower odds of responding to HGNS compared with those with a BMI of 32 or less (odds ratio, 0.25; 95% CI, 0.07-0.94). Of 44 patients who slept in a supine position, 17 (39%) achieved a treatment response, with a clinically meaningful reduction in median (IQR) supine AHI from 46.3 (33.6-63.2) events per hour preimplantation to 21.8 (4.30-42.6) events per hour post-implantation (Hodges-Lehman difference of 24.6; 95% CI, 23.1-26.5). In adjusted analysis, BMI was associated with lower odds of responding to HGNS with supine AHI treatment response (odds ratio, 0.39; 95% CI, 0.04-2.59), but the imprecision of the estimate prevents making a definitive conclusion.
"Body mass index is clearly an important factor in predicting whether hypoglossal nerve stimulation will work for an individual patient," Landsness added. "Our study shows an almost linear relationship between BMI and treatment success. For every unit of BMI increase over 32, the odds of successful treatment decrease by about 17%."
Inspire is the only FDA-approved hypoglossal nerve-stimulation device available in the United States. The company also markets the device in Europe, Japan and other countries. About 50,000 patients worldwide have been implanted with it.
Implantation of a hypoglossal nerve-stimulation device is a relatively simple outpatient surgery. Among the biggest concerns for patients are in terms of money and time. Landsness estimates that the therapy can cost from $50,000 to $100,000 out of pocket without insurance and take a year to be fully optimised.
"We have patients coming to us who really want this treatment, because they view it as a life-changing alternative to CPAP," Landsness concluded. "It certainly can work for some people, but we don't want to recommend it to patients if there's a chance their BMIs will affect the device's usefulness."
Response to hypoglossal nerve stimulation changes with body mass index and supine sleep., JAMA Otolaryngology–Head & Neck Surgery. To access this paper, please click here (login maybe required)