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

ABSTRACT

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 (nighttime SBP-daytime [corrected] SBP ratio). We defined nondipping as a nighttime [corrected] SBP-daytime [corrected] 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.