Purpose: Obstructive sleep apnea (OSA) is generally more common in men than in women, so many studies have only involved male OSA patients as subjects. However, a certain proportion of OSA patients are female, and few studies have addressed this population. Maxillofacial morphology and obesity are now being shown to be intimately connected with OSA, but the details remain unclear. The objective of this retrospective study was to identify the clinical features of OSA in men and women of different ages, with a focus on maxillofacial morphology and body mass index (BMI).Methods: The subjects comprised 112 patients (56 men and 56 women) randomly selected from adult patients in the Niigata University Medical and Dental Hospital. We investigated the results of lateral cephalogram measurements and polysomnography (PSG) conducted before the start of OSA treatment. We then divided the patients by age (with 50 years as the cutoff value) and sex, and performed statistical comparisons among these four groups.Results: The findings showed that the hyoid bone was lower in men aged >= 50 compared with <50, and the cross-sectional area of the tongue was larger. This suggested that aging changes in maxillofacial morphology may be a risk factor in men. In women, however, only slight morphological differences were found between the two age groups.Conclusions: This comparative study of sex and age groups in OSA patients suggests that the different groups have different clinical characteristics and may have different risk factors for developing OSA.