A new study highlights the connection between the supine position and the specific endotypic characteristics that exacerbate obstructive sleep apnea.

It’s well understood and accepted that sleep position, in particular the supine position in which a person sleeps on their back with their face and abdomen facing upwards, is associated with an increase in sleep-disordered breathing.

While over half of all cases of obstructive sleep apnea (OSA) are classified as supine-related, the pathological endotype during supine position is not fully understood. To better understand this phenomenon, researchers from Brigham and Women’s Hospital, Harvard School of Medicine, China Medical University Hospital, and Nox Medical teamed up to investigate the endotypic traits of supine predominant OSA and explore the variations in endotypic traits between the supine and lateral positions in Asian patients.

The researchers found that supine predominant OSA is a prevalent phenotype of OSA in Southeast Asian patients. According to the recent study, published in the European Respiratory Journal, inadequate upper airway compensation appears to be a crucial underlying pathology in patients with supine predominant OSA, according to the recent study, published in the European Respiratory Journal.

“The endotypic traits of OSA constitute a valuable tool for clinicians in guiding personalized treatment decisions, although they are not inherently accessible through standard PSG (polysomnography) yet. Our team aims to establish connections between clinical characteristics and endotypic traits, offering clinicians valuable insights. Additionally, we seek to elucidate the pathological mechanisms of OSA by investigating the positional effects on endotypic traits,” says associate principal investigator Wan-Ju Cheng, MD, PhD, of the National Health Research Institutes of Taiwan and psychiatrist at China Medical University Hospital, in a release.

The researchers recruited 689 adult patients with OSA from a single sleep center between April 2020 and December 2022. Endotypic traits, namely arousal threshold, collapsibility, loop gain, and upper airway muscle compensation, were derived algorithmically from polysomnography data. 

During the study, the researchers cross-sectionally compared demographic and endotypic traits between supine-predominant OSA and non-positional OSA. They examined the associations between supine-predominant OSA and endotypic traits.

Additionally, they compared the changes in endotypic traits between supine and lateral positions in patients with supine predominant OSA and non-positional OSA.

The results showed that 75.8% of patients were identified as having supine-predominant OSA. Compared to non-supine predominant OSA, supine-predominant OSA was associated with low collapsibility (β=-3.46, 95% confidence interval [CI]=-5.93 to -1.00) and reduced compensation (β=-6.79, 95% CI=-10.60 to -2.99).

When transitioning from the lateral to supine position, patients with supine-predominant OSA had a substantial decrease in compensation compared to those with non-supine-predominant OSA (-11.98 versus -6.28%eupnea ventilation).

Impaired upper airway dilator muscle function likely serves as the key factor in supine position-predominant OSA. Interventions aimed at improving upper airway muscle function may prove beneficial for individuals exhibiting this specific OSA phenotype, according to Wan-Ju Cheng.

“The collaboration between the Clinical Sleep Center of China Medical University Hospital, under the leadership of Dr Liang-Wen Hang, and the Nox research team has yielded fruitful results. We are currently engaged in additional studies exploring the phenotype and endotype of OSA across diverse age groups, genders, and ethnicities,” says Wan-Ju Cheng in a release.

Ingvar Hjalmarsson, president of Nox Medical and executive vice president of strategic execution, adds in a release, “This research supports our belief about how important it is for the field of sleep medicine to go beyond AHI (apnea-hypopnea index) and fully understand the different underlying causes of sleep apnea so that we can move faster towards personalized care. Every individual is different and deserves personalized care to ensure long-term success on therapy.” 

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