OBJECTIVE: To investigate the association between obstructive sleep apnea (OSA), coronary calcification and arterial stiffness in patients with diabetic nephropathy.

DESIGN AND METHOD: We conducted a cross-sectional study in patients with diabetic nephropathy. Subjects with type-2 diabetes, estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 and urine albumin-creatinine (UAC) ratio > 30 mg/g were recruited from the outpatient clinics in renal medicine or diabetes or from the local general primary care. Eligible patients were tested for OSA with ApneaLinkâ and quantified by apnea-hypopnea index (AHI, events/h). Absence of OSA was defined as AHI < 5, mild OSA as 5-14, moderate as 15-29 and severe as > = 30. Subjects with an AHI < 5 or > = 15 had a coronary computed tomography angiography (CTA) with subsequent blinded Agatston-scoring (AS) to quantify coronary calcification. Aortic stiffness was determined as carotid-femoral pulse wave velocity (cf-PWV) using Sphygmocorâ.

RESULTS: A total of 121 patients were examined by ApneaLinkâ with 114 having complete data. 43 (38%) did not have OSA, 33 (29%) had mild OSA and 38 (33%) had moderate-severe OSA. A total of 74 patients (92%) underwent CTA and 70 cf-PWV measurements. Mean age was 71 years (73% males), mean eGFR 32 mL/min and mean UAC-ratio 533 mg/g. BMI and UAC-ratio were higher in the OSA-group than the non-OSA group, while age, smoking habits, eGFR, diabetes duration, Hb1Ac, blood pressure, lipid levels, and medication were comparable between the two groups. Logarithmic transformed Ln(e) AS was significantly higher in patients with moderate-severe OSA compared to non-OSA (6.59 ± 1.71 vs. 5.56 ± 2.41, p = 0.04) and the same was observed for cf-PWV (11.9 ± 2.7 vs. 10.5 ± 2.2, p = 0.03) (Figure 1). A secondary analysis suggested AS to be especially elevated in those with severe OSA (mean AS 2350, n = 16) as compared to moderate OSA (AS 1031, n = 19) and non-OSA (AS 1011, n = 39).

CONCLUSIONS: OSA is common in patients with diabetic nephropathy and associated with increased coronary calcification and aortic stiffness. These vascular abnormalities are seen despite optimized blood pressure-, lipid- and glycemic control. Our data indicate that screening for OSA adds important cardiovascular risk information in patients with diabetic nephropathy.