Clinical characteristics of Japanese patients with familial obstructive sleep apnoea syndrome

Background and objective: Craniofacial structure and body fat are key factors that predispose to upper airway obstruction while asleep, and these phenotypes can be genetically inherited. Neither the clinical characteristics of familial obstructive sleep apnoea syndrome (OSAS) nor the definitive morphological factors responsible for familial occurrence have been well identified. This study compared the clinical and cephalographic characteristics of Japanese patients with familial OSAS, non‐familial OSAS and healthy controls, to clarify the mechanisms underlying familial OSAS. Methods: The study recruited 28 patients with familial OSAS, comprising 14 index cases and 14 first‐degree relatives affected with OSAS, and compared these with age‐ and sex‐matched patients with non‐familial OSAS (n = 32) and healthy subjects (n = 33). Data on clinical status were collected, including the presence of hypertension, BMI and daytime sleepiness measured on the Epworth sleepiness scale. Respiratory function was evaluated by the AHI, % periods in which SpO₂ fell 90% or below and lowest value of SpO₂ on polysomnograms. Information on the first witnessed age of habitual snoring during sleep was collected via interview with patients and/or their family members. A detailed cephalometric assessment was made of each study subject. Results: Patients with familial OSAS had lower mean BMI than did patients with non‐familial OSAS. The first witnessed age of habitual snoring was younger in the familial cases than the non‐familial cases. Cephalometric variables showed that the posterior airway space and the distance between the gonion and the gnathion were significantly smaller in the familial group than in the other two groups. Conclusions: Familial OSAS occurred at a younger age than non‐familial OSAS due to minor anomalies of craniofacial morphology.