Longitudinal Decline of Renal Function in Hypertensive Veterans

Abstract

Objectives: To determine the association of systolic blood pressure (SBP) and medication to renal function over time in a cohort of hypertensive veterans. Three research questions were addressed. What is the relationship between GFR and SBP in all veterans? In normotensive veterans, what is the relationship between developing hypertension and GFR? In veterans with a hypertension diagnosis, what is the relationship between controlled SBP, anti-hypertensive medications and GFR? Methods: Data were obtained from Southern Arizona Veterans' Affairs Health Care System from January 1, 2000 through December 31, 2006. Inclusion criteria consisted of veterans ≥ 21 and < 90 years of age with at least two SBP measurements and two serum creatinine measurements at least 90 days apart. Analyses were performed using a generalized linear mixed model to address serial correlation. Blood pressure, age, sex, race/ethnicity membership, diabetes, proteinuria, and risk factors for renal failure were examined. First, all eligible veterans’ GFR was modeled over seven years. Second, an inception cohort was formed with veterans who developed hypertension over the study period. Third, veterans with a hypertension ICD-9 formed time-varying controlled/uncontrolled hypertension groups. Medication categories examined in the hypertension groups included angiotensin converting enzyme inhibitor(ACE), betablocker( BB), calcium channel blocker(CCB) monotherapy, or combinations of ACE, BB, and CCB. Results: A total of 39,948 veterans were eligible for the first analysis. There were 3,036 who developed hypertension compared to 8,856 who did not in the second analysis. The third analysis consisted of 25,819 subjects: 12,411 with controlled, 13,406 with uncontrolled SBP. In each analysis, there were first-order interactions between blood pressure*age, and blood pressure*time, making interpretation of the results dependant upon these variables. Overall, GFR decreased over time, increasing blood pressure, and increasing age. ACE, BB, CCB use was associated with higher GFR (1.7, 95% CI 1.4-2.1; 1.0, 95% CI 0.7-1.4; and 0.8, 95% CI 0.3-1.3 ml/minute/1.73m², respectively). Conclusions: These analyses identified significant decrease in GFR over time. The effect of blood pressure on GFR was dependent upon time and age. Persons with controlled BP taking antihypertensive therapy had higher GFR than those taking no medication suggesting that antihypertensive medication use preserves kidney function.