Rationale: The difference in mortality from obstructive sleep apnea (OSA) by sex is an important issue. Visceral fat, a significant risk factor for cardiovascular disease, was reported to be closely related to OSA.
Objectives: To assess the different associations between OSA and visceral fat area (VFA) by sex, which might account for the different prognosis in men and women with OSA.
Methods: Participants were 271 men and 100 women consecutively hospitalized for examination of OSA from October 2008 to December 2010. Among the 371 participants, relationships were analyzed between fat areas by computed tomography, comorbidity, polysomnographic data, arterial blood gas, pulmonary function, and venous blood data. Multiple regression analyses were performed to identify variables independently associated with VFA and subcutaneous fat area for each sex.
Measurements and main results: Despite similar body mass index (BMI) and waist circumference, men had larger VFA, more severe OSA, and more severe dyslipidemia than women. Multiple regression analyses revealed that in men, not only age and BMI but also minimal oxygen saturation (contribution rate [R(2)], 4.6%) during sleep, and alveolar-arterial oxygen difference (R(2) = 7.6%) were independently associated with VFA. Conversely, VFA was associated only with BMI in women.
Conclusions: Only in men was OSA independently associated with VFA. The lesser associations between OSA and visceral fat in women might account for the lower impact of OSA on cardiovascular disease or mortality in women.