Metabolic abnormalities in obstructive sleep apnea patients

Background: Obstructive sleep apnea (OSA) is a well-recognized risk factor of cardiovascular disorders and is related to metabolic syndrome. The aim of this study was to evaluate the effect of BMI and AHI/RDI on metabolic disturbances in patients suspected of OSA.

Methods: Ninety-nine patients referred with suspected OSA underwent standard polysomnography or limited sleep study. AHI/RDI > or = 10/hour was considered relevant for OSA diagnosis. Subjects with AHI/RDI < 10 were considered as controls. We assessed apnea-hypopnea index or respiratory disturbances index (AHI/RDI), Epworth sleepiness scale (ESS), body mass index (BMI), C-reactive protein (CRP, mg/l), glycosylated haemoglobin (HbA1c, %), fasting serum total cholesterol, HDL-, LDL-cholesterol, triglycerides (TG), glucose (G), insulin (INS, IU/ml) and HOMA index.

Results: Data are presented as mean +/- SD or median (interquartile range) for parametric and nonparametric data respectively. Twenty-two patients were included as controls (age 51.8 +/- 10 vs. 55 +/- 11 in OSA; p = NS). AHI/RDI in the OSA group was 23 (16-31.3) and 7 (3.8-8.1) in controls (p < 0.001). BMI in OSA 32.2 +/- 5.8 vs. 30.4 +/- 4.6 in controls (p = NS). Patients with OSA had higher TG (160 +/- 75.9 vs. 130.2 +/- 51.9 mg/dl, p = 0.046), G (5.04 +/- 0.6 vs. 4.47 +/- 0.6, p = 0.0037), HOMA (2.31 +/- 1.5 vs. 1.85 +/- 1.7, p = 0.046). G correlated best with AHI/RDI (p < 0.001, r = 0.41). Significant differences were observed in OSA patients between obese (51 pts, BMI 35.2 +/- 4.8) and non-obese (26 pts, BMI 26.61 +/- 1.9) pts in: HDL-cholesterol (50.8 +/- 13.2 vs. 60.9 +/- 18.4 mg/dl; p = 0.02), TG (178.7 +/- 69.9 vs. 124 +/- 75.3 mg/dl, p < 0.001), G (5.15 +/- 0.7 vs. 4.8 +/- 0.5 mmol/l, p = 0.01), INS (11.7 +/- 5.9 vs. 6.57 +/- 4.7, p < 0.001), HOMA (2.7 +/- 1.4 vs. 1.4 +/- 1.2, p < 0.001), HbA(1c) (5.89 +/- 0.9 vs. 5.4 +/- 0.8, p = 0.03), CRP (2.2 +/- 2.9 vs. 1.09 +/- 1.2, p = 0.01).

Conclusions: Our findings support the results of previous studies showing the influence of OSA alone on metabolic disturbances. However, BMI has major impact on metabolic variables.