Relation between circadian blood pressure rhythm and serum albumin level in non-diabetic patients with proteinuria

It remains unclear whether the abnormal circadian blood pressure (BP) rhythm in non-diabetic chronic kidney disease (CKD) is related to hypoalbuminemia. We evaluated relationships between circadian BP rhythm and serum albumin concentration (SAC) and also examined autonomic nervous activities. Non-diabetic CKD patients with proteinuria (n=197; 105 men, 92 women; aged 47.0 +/- 13.3 years; estimated glomerular filtration rate30 ml/min) were divided into nephrotic syndrome (NS: n=46, SAC30 g/l), hypoalbuminemia (n=65, 30<SAC<40 g/l) and normoalbuminemia (n=86, SAC40 g/l) groups. Non-proteinuria subjects (n=97, urinary protein/creatinine ratio<30mg/g creatinine) were enrolled as the non-proteinuria group. Ambulatory 24 h BP monitoring was conducted in all subjects. Simultaneously, power spectral analysis of heart rate was performed to evaluate the sympathovagal balance. Waking BP was lower in the hypoalbuminemia and NS groups than the other groups. Sleeping/waking mean BP ratio was not different between non-proteinuria (0.87 +/- 0.07) and normoalbuminemia (0.89 +/- 0.08) groups, but increased significantly (p<0.05) in the hypoalbuminemia (0.92 +/- 0.08) and NS groups (0.96 +/- 0.08). Significant reverse correlations were observed between SAC and sleeping/waking mean BP ratio (r=-0.274, p<0.001) in all patients. Multivariate regression analysis identified SAC and sympathovagal balance as predictors of increased sleeping/waking BP ratios as the dependent variable. In non-diabetic CKD patients with proteinuria, disturbed circadian BP rhythms were related to SAC and 24 h sympathovagal imbalance.