0499 The Relationship Between Tongue Force, OSA and Upper Airway Anatomy, Assessed by MRI

Introduction The pathogenesis of obstructive sleep apnea (OSA) is multifactorial and likely involves reduced activation of upper airway (UA) dilator muscles during sleep. The genioglossus, the primary tongue protrusor, contracts with each inspiration to prevent posterior tongue collapse and maintain airway patency. Several OSA therapies target tongue musculature; however, the impact of tongue protrusion strength on OSA severity remains poorly defined. Prior studies examining this relationship lacked comprehensive characterization of UA anatomy, overlooking key structural confounders. Our study aimed to define the relationship between tongue protrusion strength and OSA severity while accounting for tongue volume and fat, as quantified by magnetic resonance imaging (MRI). Methods The sample included 219 participants from the EXPO study, a multicenter, international, case-control study of adults with moderate-to-severe OSA (apnea-hypopnea index [AHI] > 15 events/hr) and controls (AHI < 15). Tongue protrusion strength was derived from the mean of four maximal isometric pressure trials with a pressure transducer. UA anatomy was quantified by MRI, including genioglossus volume, total tongue volume, and fat percentage of tongue. Tongue force measurements were compared between apneics and controls using Pearson correlations (unadjusted) and linear regression adjusted for age, gender, BMI, race, and site. Results Participants were predominantly male (59.4%) with mean age 51.4 years, BMI 30.5 kg/m2, and AHI 22.9 events/hour (135 apneics, 84 controls). Maximal tongue force was not associated with OSA status or severity, in either adjusted or unadjusted analyses. Similarly, in both unadjusted and adjusted analyses, maximal tongue force was not correlated with genioglossus volume, total tongue volume, or tongue fat percentage. Comparisons between apneics and controls showed no significant correlations between maximal tongue force and any of the three anatomic tongue metrics, regardless of adjustment. Conclusion This study is the first to use quantitative MRI of the UA to examine the relationship between tongue strength and OSA severity. Overall, our results indicate that maximal tongue force alone does not explain OSA severity. These findings underscore the importance of considering that tongue strength also includes fatiguability, which may contribute to OSA pathogenesis and inform the development of targeted therapies. Support (if any) NIH Grants P01 HL094307, P01 HL160471, F32HL182221; ATS ASPIRE Fellowship.