Cardiorespiratory fitness and obstructive sleep apnea syndrome in morbidly obese patients

Background: Conflicting data exist regarding the effects of obstructive sleep apnea syndrome (OSAS) on cardiorespiratory fitness in morbidly obese individuals with normal resting left ventricular function. Methods: Ninety-two morbidly obese subjects without any prior diagnosis of OSAS undenvent cardiorespiratory fitness testing, two-dimensional echocardiography, and overnight polysomnography. Using the results of the polysomnogram, comparisons were made between subjects with (n = 42) and without (n = 50) OSAS. Results: Mean body mass index (BMI) for the study population (n = 92) was 48.6 +/- 9.3 kg/m(2) ( +/- SD); mean age was 45.5 +/- 9.8 years, and approximately 69% were female. Despite having a higher resting, exercise, and resting mean arterial pressures, the OSAS cohort had a maximum oxygen consumption that was lower than the cohort without OSAS (21.1 mL/kg/min vs 17.6 mL/kg/min; p < 0.001). There was no difference in BMI, age, gender, waist circumference, and neck circumference between those with and without OSAS. Differences were observed between the cohorts in systolic BP, diastolic BP, and heart rate during rest, exercise, and recovery periods. There was no difference in ejection fraction, diastolic dysfunction, and treadmill test duration between cohorts. Conclusions: Morbidly obese individuals with OSAS demonstrate reduced cardiorespiratory fitness and differing hemodynamic responses to exercise testing as compared with their counterparts without this disorder. These data suggest chronic sympathetic nervous system activation negatively influences aerobic capacity in OSAS.