Cross-sectional study on the relationship between the level of serum cystatin C and blood pressure reverse dipping in hypertensive patients

Objective: To investigate the relationship between the level of serum cystatin C (s-CC) and reverse-dipper blood pressure (BP) pattern. Design: Cross-sectional study. Setting: Single centre. Participants: A total of 718 hypertensive patients were eventually recruited from cardiac clinics between 2012 and 2014 in the Second Affiliated Hospital, Xi'an Jiaotong University. They were diagnosed as essential hypertension according to their casual office records of systolic blood pressure (SBP) and/or diastolic blood pressure (DBP). Patients were excluded if they were <18 or >90 years old, under antihypertensive treatment, night workers, suffering from acute stroke or myocardial infarction within the past 6 months, diagnosed as secondary hypertension, sleep apnoea or other sleep disorders, renal failure, cardiac failure, chronic obstructive pulmonary disease, women during pregnancy or intolerant to the ambulatory BP monitoring (ABPM). Measurement: The selected patients were evaluated with 24 hours ABPM. Peripheral venous blood samples were collected to evaluate the s-CC levels by ELISA. Methods: The distribution of hypertensive patients with different levels of s-CC among each circadian BP pattern group was analysed using analysis of variance. Multinomial logistic regression analysis was applied to explore the relationship between the relevant variables and ABPM results. Results: S-CC level in reverse-dipper group (1.19 +/- 0.53 mg/L) was increased significantly when compared with dipper group (1.06 +/- 0.36 mg/L) (p=0.021). In addition, after multinomial logistic regression analysis, s-CC (OR 1.717; 95% CI 1.033 to 2.854; p=0.037) and diabetes (OR 2.313; 95% CI 1.401 to 3.821; p=0.01) were significantly different between the reverse-dipper group and dipper group. On the other hand, the decline rate of nocturnal SBP (r=-0.117; p=0.002) and DBP (r=-0.089; p=0.018) was negatively correlated with the s-CC level. Conclusions: The s-CC level was significantly higher in the reverse-dipper group than the dipper group and that s-CC was associated with the reverse-dipper pattern of BP examined with 24 hour ABPM.