Abstract 3001: Longitudinal Pulse Pressure is a Better Predictor of 24-Hour Urinary Albumin Excretion than Other Indices of Blood Pressure: The Baltimore Longitudinal Study of Aging
Urinary albumin excretion (UAE) is a marker of renal microvascular injury in hypertension. High flow and low resistance of the renal arterial bed expose the glomeruli to high pulsatile stress, which may contribute to glomerular injury in hypertension. Indeed, UAE is significantly associated with pulse pressure (PP) in cross-sectional studies. However, the longitudinal relationship of PP with UAE and its importance relative to other indices of blood pressure (BP) are not well defined. We hypothesized that longitudinal PP is a predictor of UAE with a better predictive power than longitudinal systolic (SBP), diastolic (DBP) or mean (MBP) BP. UAE was measured in 24-hour urine collections from 521 community dwelling volunteers in the Baltimore Longitudinal Study of Aging who were free from macroalbuminuria (UAE > 200 μg/min) and were not on antihypertensive therapy. Subjects underwent serial measurements of BP and other variables during the 5.9 ± 4.7 years preceding the UAE measurement. Cumulative exposure was estimated as the area under the curve of serial measurements (median = 5) divided by the number of follow-up years for each subject. In the cohort (age = 57 ± 15 years, 55% women, 17% Black, 31% hypertensive), median [IQR] UAE was 4.8 [3.6 – 8.9] μg/min. At the time of UAE measurement, SBP, DBP, MBP, and PP were 127 ± 20, 79 ± 11, 95 ± 12, and 48 ± 16 mm Hg, respectively. UAE correlated modestly with longitudinal SBP, DBP, MBP, and PP in men (r = 0.23, 0.16, 0.21, and 0.29, respectively; all P < .02), but not in women (r = 0.01, 0.00, 0.01, and −0.04, respectively; all P ≥ .57). In men, in separate longitudinal regression models that adjusted for potential confounders and included either SBP and DBP or MBP and PP, UAE was independently associated with SBP (β = 0.22, P = .03) and PP (β = 0.28, P = .001), but not with DBP (β = −0.07, P = .43) or MBP (β = 0.03, P = .72). In a stepwise regression model predicting UAE in men that adjusted for confounders and offered all 4 longitudinal indices of BP, PP was the only index of BP to enter the model. Longitudinal exposure to high pulsatile stress is an important predictor of UAE in men. Future studies should examine whether PP is a better therapeutic target than other indices of BP for preventing hypertensive nephropathy.