The impact of obesity on cardiac dysfunction in patients with sleep-disordered breathing

Introduction Obesity and heart failure are strongly associated with sleep-disordered breathing (SDB). However, the determinants of cardiac dysfunction in patients with SDB are not known. Methods We studied 90 patients suspected of having SDB (66% women and 67% black), age 50.4 +/- 13.4 years and body mass index (BMI) 38.6 +/- 9.8 kg/m(2). Apnea-hypopnea index (AHI) and nadir pulse oximetry (SpO(2)) were determined by polysomnography recordings. Left atrial (LA) diameter and left ventricular posterior wall (LVPW) thickness were determined by echocardiography. Patients who had EF<50 %, estimated right ventricular systolic pressure >45 mmHg or valvular heart disease were excluded. Results Univariate analysis revealed a positive correlation between LA diameter and each of BMI, neck circumference (NC), and AHI (coefficients, 0.28, 0.34, and 0.36, respectively; p<0.05). Multivariable linear regression analysis revealed that BMI was the only independent predictor of LA enlargement (coefficient 0.02, p<0.05). LVPW thickness correlated with BMI, NC, and AHI (correlation coefficients were 0.43, 0.47, and 0.33, respectively; p<0.05). Multivariable linear regression analysis revealed a significant relationship between LVPW thickness and each of BMI and NC (coefficients 0.016 and 0.007, respectively; p<0.05) but not AHI. BMI and LVPW associated with nadir SpO2 (r=-0.60, p<0.01 and r=-0.21, p=0.05; respectively), and BMI was a predictor of nadir SpO2 during sleep (B=-0.59; CI: -0.84, -0.33; p=0.01). Conclusions Obesity can predict cardiovascular morbidity and nocturnal hypoxemia independent of the severity of the SDB. Our findings suggest the independent contribution of excess body weight on cardiac dysfunction and hypoxia in SDB patients.