Obstructive sleep-disordered breathing, including obstructive sleep apnea (OSA), represents a significant yet underdiagnosed condition in the pediatric population, particularly among adolescents with obesity. The tongue is a central anatomical contributor to upper airway collapsibility; however, its biomechanical properties have been investigated almost exclusively in adult populations, leaving a critical gap in knowledge regarding younger individuals.
This study aims to assess tongue biomechanical and echographic characteristics using quantitative ultrasound modalities - shear-wave elastography (SWE), acoustic attenuation, and echo intensity - in adolescents aged 12 to 18 years with obesity and obstructive sleep disorders. The study adopts a mixed design combining (1) an observational cross-sectional comparison between participants with obesity and OSDB and age- and sex-matched healthy controls at baseline, and (2) a prospective longitudinal cohort component evaluating changes in tongue ultrasound characteristics over the course of a 30-week multidisciplinary inpatient weight-loss program delivered as standard care at the Zeepreventorium (De Haan, Belgium). An additionnal methodological objective consists in determining intra-rater and inter-rater reliability of the ultrasound acquisition protocol providing a reproducible framework for future studies.
Aged 12-18 years
Already enrolled in Zeepreventorium weight-loss program as Standard Care Diagnosed Obstructive Sleep Apnea (AHI ≥ 1)1 or any Obstructive sleep disordered breathing detected by any of the specific sleep questionnaire (OSA-18, ESS, SSS-Ad, PDSS)
Any other orthopedic, traumatic, or rheumatologic condition affecting the cervicocephalic region
Syndromic or neuromuscular disorders
Cognitive impairment limiting compliance with study procedures
Inability to provide informed consent
Crossover
Submental ultrasound
DeviceTongue ultrasound via a submental approach. This non-invasive, pain-free and non-radiating protocol will study both morphological and dynamic characteristics of the tongue. Ultrasonographic assessment will be performed with participants in a resting, supine position and ultrasound gel will be used to optimise submental probe contact.
Tongue stiffness
Tongue stiffness is measured by shear-wave elastography and expressed in kPa.
Tongue thickness
Tongue thickness (expressed in cm) will be measured with ultrasound as the perpendicular distance from the deep fascia of the geniohyoid muscle to the highest lingual dorsum in the midsagittal plane
Echo Intensity
Echo intensity will be measured with ImageJ / Fiji software (ImageJ, US NIH, Bethesda, USA) and refers to the mean value of pixels of an area, based on a grey scale between 0 (black) and 255 (white)
Acoustic Attenuation
Attenuation will be measured with ultrasound and depicts the quantitative measurement of ultrasound attenuation in tissues. It is expressed as an attenuation coefficient in dB/cm/MHz.
Intraclass correlation coefficient, ICC
Intraclass correlation coefficient will be used to assess intra and inter-rater reliability of ultrasound markersUltrasound reliability and repeatability of tongue measurements will be assessed with intraclass correlation coefficients (ICC), along with their 95% confidence intervals. Each ultrasound measurement (tongue size and morphological parameters, echo intensity, stiffness, tissue attenuation imaging, tissue scatter distribution imaging, and fat fraction) in sagittal and coronal planes will be performed twice in fifteen participants by the principal investigator, with a 24-hour interval between examinations.
OSA-18 questionnaire
The OSA-18 is a disease-specific screening tool for early diagnosis of obstructive sleep apnea in children, and is used to evaluate the quality of life before and after treatment. The Obstructive Sleep Apnea - 18 questionnaire is specific to obstructive sleep apnea in children and will be used for correlation analysis. Quality of life is assessed using the Obstructive Sleep Apnea - 18 Quality of Life Survey (OSA-18), a validated questionnaire comprising 18 items. Total scores range from 18 to 126, with higher scores indicating poorer quality of life and greater disease impact, and lower scores reflecting better outcomes.
Stanford Sleepiness Scale (for adolescents)
The Stanford Sleepiness Scale (SSS) is a single-item, momentary self-report scale assessing current level of alertness and sleepiness on a 7-point ordinal scale, ranging from 1 ("feeling active, vital, alert, or wide awake") to 7 ("no longer fighting sleep, sleep onset soon, having dream-like thoughts"). Originally developed by Hoddes et al. (1973), the scale captures state sleepiness at a given moment rather than habitual sleepiness patterns, making it particularly suitable for repeated within-session assessments. Its adaptation and use in adolescent populations has been documented in pediatric sleep research, where it complements trait-level instruments such as the ESS and PDSS.
Pediatric Daytime Sleepiness Scale (PDSS)
The Pediatric Daytime Sleepiness Scale (PDSS) is an 8-item self-report questionnaire designed to assess daytime sleepiness in school-aged children and adolescents. Each item is rated on a 5-point Likert scale (0-4), yielding a total score ranging from 0 to 32, with higher scores indicating greater daytime sleepiness. The PDSS was developed and validated by Drake et al. (2003) and has demonstrated adequate internal consistency (Cronbach's α = 0.78) and convergent validity with objective sleep measures. It is specifically designed for pediatric populations and captures sleep-related daytime impairment across academic, behavioral, and social domains. A score ≥ 15 has been proposed as a clinically meaningful threshold for excessive daytime sleepiness in adolescents.
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