Prospective study of the effect of blood pressure on renal function in old age: the Leiden 85-Plus Study.

High BP is associated with decline of renal function. Whether this is true for very old people largely is unknown. Therefore, this study assessed the effect of BP on creatinine clearance over time in very old participants. A total of 550 inhabitants (34% men) of Leiden, The Netherlands, were enrolled in a population-based study at their 85th birthday and followed until death or age 90. BP was measured twice at baseline and at age 90 yr. Creatinine clearance was estimated annually (Cockcroft-Gault formula). The mean creatinine clearance at baseline was 45.4 ml/min (SD 11.5). Systolic BP was not associated with changes in creatinine clearance during follow-up. Those with diastolic BP (DBP) <70 mmHg had an accelerated decline of creatinine clearance (1.63 ml/min per yr) compared with those with DBP between 70 and 79 mmHg (1.21 ml/min per yr; P = 0.01), 80 to 89 mmHg (1.26 ml/min per yr; P = 0.03), and >89 mmHg (1.38 ml/min per yr; P = 0.32). Participants with a decline in systolic BP during follow-up had an accelerated decline of creatinine clearance compared with those with stable BP (1.54 [SE 0.09] versus 0.98 ml/min per yr [SE 0.09]; P < 0.001). Similar results were found for a decline in DBP (1.54 [SE 0.10] versus 1.06 ml/min per yr [SE 0.08]; P < 0.001). In the oldest individual, high BP is not associated with renal function. In contrast, low DBP is associated with an accelerated decline of renal function. The clinical implications of these findings have to be studied.