Albuminuria and renal function in obese adults evaluated for obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with hypertension, obesity and metabolic syndrome that are risk factors for cardiovascular and chronic kidney disease. Few data are available regarding renal parameters in patients with OSA.

We conducted a cross-sectional study of 91 obese adults who had routine polysomnography before bariatric surgery. Presence and severity of OSA were determined by the apnea-hypopnea index (AHI <5 = no OSA and AHI > or = 5 = OSA). Clinical and laboratory data were available within a month of polysomnography.

Mean +/- SD age was 44.9 +/- 9.9 years. There were 66 women. Mean +/- SD body mass index was 48.3 +/- 8.9 kg/m2 with hypertension and type 2 diabetes present in 55 and 31 subjects, respectively. There were 36 subjects with no OSA and 55 with OSA. The two groups had similar demographic characteristics, blood pressure (BP), lipid profile and medication use except for difference in mean +/- SD hemoglobin A1c (5.6 +/- 0.6% in no OSA, 6.0 +/- 0.8% in OSA; p = 0.029) and use of renin-angiotensin system blocking agents (22.2% in no OSA, 46.4% in OSA; p = 0.024). Median (interquartile range) urine albumin:creatinine ratio (ACR) was not different between the two groups [6 (4-14.5) mg/g in no OSA, 8 (5-16) mg/g in OSA; p = 0.723], while significant difference existed in serum creatinine (0.8 +/- 0.2 mg/dl in no OSA, 0.9 +/- 0.2 mg/dl in OSA, p = 0.013). Age- and gender-adjusted correlations were observed between log-log ACR and systolic BP (r = 0.265; p = 0.016), log-log ACR and diastolic BP (r = 0.245; p = 0.026) and between serum creatinine and log AHI (r = 0.188, p = 0.089). Multiple linear regression analysis demonstrated log-log ACR to be associated with diastolic BP (p = 0.046), while serum creatinine was associated with log AHI (p = 0.044).

In obese adults, increasing severity of OSA is associated with higher serum creatinine but not greater degree of albuminuria.