We aim to examine the relationship between visit-to-visit systolic blood pressure variability (BPV) and decline in renal function in patients with hypertension and determine the level of systolic BPV that contribute to significant renal function decline.Design and method:
This is a 15-year retrospective cohort study of 904 hypertensive patients (1998–2012) in a primary care clinic. Three monthly blood pressure readings per year were retrieved from the 15 years of clinic visits. We used standard deviation (SD) and coefficient of variation (CV) as measures of systolic BPV. Serum creatinine was captured and eGFR was calculated at baseline, 5-year, 10-year and 15-year. Rate of renal function decline was estimated by fitting a linear regression line through the eGFR measurements for each individual patient and expressed as eGFR slope.Results:
A total of 904 hypertensive patients with 15-year of clinic follow up were entered into analysis. The mean SD of SBP was 14.3 ± 3.13 mmHg and CV of SBP was 10.3 ± 2.0%. Mean for eGFR slope was −0.96 ± 1.5 ml/min/1.73 m2/year. There was significant relationship between BPV and slope of eGFR (SD of SBP r = −0.16, p < 0.001; CV of SBP r = −0.14, p < 0.001, using Pearson's correlation). In multiple regression analyses, BPV (SD and CV) for SBP and mean SBP for each individual was significantly associated with eGFR slope after adjustment for confounders. Using receiver operating characteristics curve (ROC) and maximum Youden index, the cutoff values as indicator for the onset of CKD for SD of SBP was 13.5 mmHg (sensitivity 69%, specificity 50%). and CV of SBP was 9.74% (sensitivity 68%, specificity 48%).Conclusions:
Our study has demonstrated that long-term visit-to-visit variability of SBP is an independent determinant of renal deterioration in patients with hypertension. Hence, every efforts should be made to reduce the BPV in order to slow down the decline of renal function in patients with hypertension.