Objective To test the hypothesis that children with Prader-Willi syndrome (PWS) and obstructive sleep apnoea syndrome (OSAS) have hypercapnia for higher proportion of total sleep time (TST) than non-syndromic children with similar obstructive apnoea–hypopnoea index (OAHI).
Design Cross-sectional study.
Setting Two tertiary care hospitals.
Patients Patients with PWS and non-syndromic children with snoring who underwent polygraphy and were of similar age, body mass index (BMI) z-score and OAHI.
Main outcome measure The two groups were compared regarding %TST with transcutaneous CO2 (PtcCO2) >50 mm Hg. The interaction between PWS diagnosis and OSAS severity (OAHI <1 episode/h vs 1–5 episodes/h vs >5 episodes/h) regarding %TST with PtcCO2 >50 mm Hg was tested using multiple linear regression.
Results 48 children with PWS and 92 controls were included (median age 2.3 (range 0.2–14.1) years vs 2.2 (0.3–15.1) years; BMI z-score 0.7±1.9 vs 0.8±1.7; median OAHI 0.5 (0–29.5) episodes/h vs 0.5 (0–33.9) episodes/h; p>0.05). The two groups did not differ in %TST with PtcCO2 >50 mm Hg (median 0% (0–100%) vs 0% (0–81.3%), respectively; p>0.05). However, the interaction between PWS and OSAS severity with respect to duration of hypoventilation was significant (p<0.01); the estimated mean differences of %TST with PtcCO2 >50 mm Hg between children with PWS and controls for OAHI <1 episode/h, 1–5 episodes/h and >5 episodes/h were +0.2%, +1% and +33%, respectively.
Conclusion Increasing severity of upper airway obstruction during sleep in children with PWS is accompanied by disproportionately longer periods of hypoventilation when compared with non-syndromic children with similar frequency of obstructive events.
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FA and H-LT contributed equally.
Contributors FA, H-LT and MM have contributed to the study concept and design and data analysis, and they have revised the initial and last draft of the manuscript critically for important intellectual content. VN, TC and AL have contributed to the study concept and design, and data acquisition and analysis, and they have revised the manuscript critically for important intellectual content. NB, EC and MS have contributed to the study concept and design and data analysis, and they have revised the manuscript critically for important intellectual content. AGK has conceptualised and designed the study, contributed to data analysis, drafted the initial manuscript and prepared the final version of the manuscript. All authors have approved the version to be submitted and published and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AGK has full access to all the data in the study and assumes responsibility for the integrity of the data and the accuracy of the data analysis.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Ethics approval The study protocol was approved by the Health Research Authority, UK (REC reference 17/LO/0753, IRAS project ID 187417) and the local research offices of the two hospitals.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement There are no additional unpublished data.