The relationship of insulin resistance, obesity and sleep-disordered breathing

Abstract

Background Obesity, in particular abdominal obesity, is an established determinant of insulin resistance. There is growing evidence supporting a causal contribution of OSA on insulin resistance (1,2), independent of obesity. This prospective cohort study further investigated the relationship of abdominal fat, insulin resistance and sleep apnea. Methods Subjects were recruited from our sleep laboratory. Demographic and anthropometric data were collected. Overnight 16-channel polysomnography was performed. Insulin resistance was estimated by the Short insulin tolerance test (SITT), and was indicated by the rate of decline in blood glucose (K constant). Fasting serum cortisol and lipid profile (cholesterol, triglyceride, LDL & HDLcholesterol, fatty acid, Apolipoproteins A & B) were measured. Overnight 12-hour urine was collected to measure catecholamines. MRI scan of abdomen was performed to quantify the amount of visceral and subcutaneous fat at three levels of the abdomen. The Results 55 men, aged 21–65, BMI 27.2+/-4.6, AHI 30.1+/-5.2 were recruited. There were significant linear relationships of insulin resistance with AHI, arousal index, O2sat < 90%, urinary norepinephrine, waist circumference, BMI, body fat, HDL-cholesterol and triglyceride (P < 0.05). Multiple linear regression analysis showed that AHI (P < 0.001) and abdominal fat (P < 0.001)/waist circumference (P < 0.005)/BMI (P < 0.001) were independent predictors of insulin resistance. Conclusion Sleep disordered breathing reflected by AHI was a determinant of insulin resistance, independent of obesity reflected by detailed quantification of body fat. The findings further support a causal role of sleep apnea on insulin resistance. References 1 Ip M.S.M., Lam B., Ng M.M., et al. Obstructive sleep apnea is independently associated with insulin resistance. Am J Respir Crit Care Med 2002;165(5):670–6. 2 Punjabi N.M., Sorkin J.D., Katzel L.I., et al. Sleep-disordered breathing and insulin resistance in middle-aged and overweight men. Am J Respir Crit Care Med 2002;165(5):677–82. This project was supported by the Lee Wing Tat Cardiorespiratory Research Grant, The University of Hong Kong.