Visceral fat accumulation as an important risk factor for obstructive sleep apnoea syndrome in obese subjects

Objectives. It is well known that obstructive sleep apnoea (OSA) is frequently associated with obesity. In the current study, we investigated the correlation between abdominal visceral fat accumulation and the presence of OSA in obese subjects. Subjects. A consecutive series of 37 patients (17 men and 20 women) with primary obesity who were admitted to the Second Department of Internal Medicine, Osaka University Hospital, were investigated. Patients with OSA were designated as those whose apnoea index (number of apnoea h(-1) of sleep) was more than 5. Main outcome measures. The distribution of body fat was determined using computed tomographic sections. The upper airway dimensions were evaluated with indices obtained by cephalometry in both inspiratory and expiratory phases. Results. Visceral adipose tissue (AT) area which was measured at the level of the umbilicus, and its ratio to total AT area were both significantly greater in OSA patients as compared with those in non-OSA patients. All subjects whose visceral AT area measured more than 220 cm(2) manifested OSA. These two parameters also closely correlated with an increase in apnoea index. A multiple linear regression analysis revealed that the visceral AT area significantly correlated to apnoea index when age, AT mass and lean body mass were taken into account. The fluctuations of the upper airway were significantly greater in the large visceral fat group than in the small visceral fat group. Conclusions. These results suggest that visceral fat accumulation is an important risk indicator for OSA in obese subjects.