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Use of hypoglossal nerve stimulation (HGNS) may be effective for treating obstructive sleep apnea (OSA), but a higher body mass index (BMI) and supine sleeping position may decrease effects, according to a retrospective cohort study.

In a cohort of 76 patients, 78% achieved a treatment response with HGNS, with a clinically meaningful reduction in median Apnea-Hypopnea Index (AHI), from 29.3 events per hour pre-implantation to 5.3 events per hour post-implementation (Hodges-Lehman difference 23.0, 95% CI 22.6-23.4), reported Eric Landsness, MD, PhD, of the Washington University School of Medicine in St. Louis, and co-authors.

However, in adjusted analyses, patients with a BMI of 32 to 35 had 75% lower odds of responding to HGNS compared with those who had a BMI of 32 or less (OR 0.25, 95% CI 0.07-0.94), they noted in .

Of the 44 patients who slept in a supine position, 17 achieved a treatment response, with a clinically meaningful reduction in median supine AHI from 46.3 events per hour pre-implantation to 21.8 events per hour post-implantation (Hodges-Lehman difference 24.6, 95% CI 23.1-26.5).

BMI was also associated with supine AHI treatment response after adjusting for post-implantation sleep position (OR 0.39, 95% CI 0.04-2.59).

Daniel Paul Vena, PhD, of Brigham and Women's Hospital and Harvard Medical School in Boston, told 番茄社区app that the risks of not having a response to HGNS are important to describe to patients. He said that encouraging weight loss can be important, as achieving a BMI under 32 improves chances of treatment response, but having a higher BMI doesn't rule it out entirely.

"It's not as though people should avoid HGNS if they have a BMI of above 32; it's just that the risk of non-response should be adequately or appropriately communicated to the patient," he added.

Ryan Soose, MD, of the University of Pittsburgh Medical Center, noted that there is evidence of several treatments proving less effective in the supine position, and that using a multifaceted treatment approach for factors like sleeping position and BMI may be the way forward for treating OSA.

"Whether it's surgery of the upper airway, dental appliances, or hypoglossal nerve stimulation -- in general, there's reduced effectiveness when people are sleeping on their back," he told 番茄社区app. "And this [research] further supports that as well. So just like the adjunctive role with weight loss, this suggests that there's probably an adjunctive role for trying to keep people off of their back."

"I think, overall, what this at least suggests is that clinicians really need to be mindful of the different variations of sleep apnea," he said. "And they shouldn't just treat with hypoglossal nerve stimulation in isolation, we should be thinking about nerve stimulation with weight loss, with optimizing sleep position, to really get the best results long term."

Landsness and team noted that traditional treatment approaches for OSA, such as continuous positive airway pressure (CPAP) therapy, oral appliances, and surgical interventions "are hindered by challenges related to patient adherence and limited response to treatment. HGNS is an alternative therapy for patients with OSA who cannot tolerate CPAP."

A HGNS device is implanted underneath the patient's skin and operates, often remotely, to stimulate the hypoglossal nerve, which runs from the back of the skull to the underside of the tongue. Treatment detects inhalation during the course of sleep and stimulates the nerve, which then dilates the airway. The treatment, which has been approved by the FDA for a decade, is often among the options discussed with patients who did not find success with CPAP.

David Kent, MD, of Vanderbilt University Medical Center in Nashville, Tennessee, told 番茄社区app via email that the results of the study are in line with the current understanding of the many factors that can impact OSA.

"Lung volumes decline precipitously when patients shift into the supine position, which further destabilizes the upper airway, reducing cross-sectional area and making it more collapsible," he wrote. "Other data suggest that when HGNS therapy fails, it's because patients have persistent collapse of the soft palate and possibly the oropharyngeal lateral walls."

"It follows that patients that have greater baseline collapsibility of these airway structures might be less likely to respond to HGNS therapy," he added. "It also fits with prior research findings that patients with complete circumferential palatal collapse (a more collapsible palate) are less likely to respond to therapy."

For this study, 76 patients with OSA implanted with HGNS at the Washington University Medical Center from April 2019 to January 2023 were included. Median age was 61, 75% were men, and 93% were white.

Prior to implantation, median AHI score was 29.3, and median supine AHI score was 46.1. OSA was mild to moderate in 51% of patients, and 62% had supine-dependent OSA. Sleep studies were conducted prior to implantation -- 46% of patients had a home sleep apnea test and 54% had a polysomnogram.

After implantation, 62% of patients predominantly slept in a lateral position, while 38% used a predominantly supine position.

The retrospective nature of the study, as well as its mostly male, white patient population and a "lack of subjective rating scales to complement the objective changes in AHI," were limitations, the authors noted.

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