Association of impaired diurnal blood pressure variation with a subsequent decline in glomerular filtration rate

Background: Most healthy people exhibit a decrease in systolic blood pressure (SBP) at night. A drop of less than 10% from mean daytime values (nondipping) is associated with chronic kidney disease, insulin resistance, and cardiovascular events. Whether nondipping precedes a decline in renal function remains unclear. We hypothesized that nondipping would predict a decline in the glomerular filtration rate ( GFR) over time. Methods: Consecutive patients referred for ambulatory blood pressure monitoring were included in our retrospective cohort if they had a serum creatinine level noted at the time of their ambulatory blood pressure recording and a follow-up creatinine level recorded at least 1 year later. Mean day and night SBPs were compared ( daytime SBP-nighttime SBP ratio). We defined nondipping as a daytime SBP-nighttime SBP ratio higher than 0.90. The GFR was calculated using the Modification of Diet in Renal Disease 4-variable equation. Results: Of 322 patients included, 137 were dippers and 185 were nondippers; their mean baseline GFRs were 80.5 mL/min per 1.73 m(2) and 76.4 mL/ min per 1.73 m(2), respectively. During a median follow-up of 3.2 years, the GFRs remained stable among dippers ( mean change, 1.3%) but declined among nondippers ( mean change, -15.9%) ( P <. 001). The creatinine levels increased by more than 50% in 2 dippers ( 1.5%) and in 32 nondippers ( 17.3%) ( P <. 001). These findings persisted after adjustment for other predictors of GFR decline. Conclusion: Blunted diurnal blood pressure variation is associated with a subsequent deterioration in renal function that is independent of SBP load and other risk factors for renal impairment.