African American Study of Kidney Disease and Hypertension Cohort Study (AASK Cohort)

General Description

The African American Study of Kidney Disease and Hypertension Cohort Study (AASK Cohort) is a prospective, observational study that is an extension of the AASK Clinical Trial, which investigated the effects of two levels of blood pressure (BP) control and the use of thre antihypertensive durg regimens on the progression of chronic kidney disease. The overall objective of the AASK Cohort Study was to determine prospectively the long-term course of kidney function and risk factors for chronic kidney disease (CKD) progression in African-Americans with hypertension-related CKD receiving antihypertensive therapy and a low blood pressure goal. A secondary objective was to determine the occurrence of cardiovascular disease and assess its risk factors in the setting of hypertension-related CKD.

Of the 1,094 randomized participants of the AASK Trial, 691 individuals who had not yet reached end-stage renal disease (ESRD) enrolled in the AASK Cohort study. Antihypertensive therapy in the cohort study was largely based on AASK trial phase results and prevailing recommendations. Ramipril, a renin-angiotensin system (RAAS)-blocker, was first-line therapy; if ramipril was not tolerated, an angiotensin receptor blocker (ARB) was used. Additional drugs were added as needed if the BP goal of <130/80 mm Hg was not achieved with ramipril. The primary renal outcome measure was a composite clinical outcome defined by doubling of serum creatinine, ESRD, or death. Cardiovascular events were also measured as a major outcome of interest. The study found that most participants with hypertensive CKD who were treated with the BP therapy continued to progress during the long term.

Objectives

The overall objective of the AASK Cohort Study was to determine prospectively the long-term course of kidney function and risk factors for chronic kidney disease (CKD) progression in African-Americans with hypertension-related CKD receiving recommended antihypertensive drug therapy within the setting of a low blood pressure goal. A secondary objective was to determine the occurrence of cardiovascular disease and assess its risk factors in the setting of hypertension-related CKD.

Outcome Measure

The primary renal outcome measure was a composite clinical outcome defined by doubling of serum creatinine, ESRD, or death. Cardiovascular events were also measured as a major outcome of interest.

Criteria

The eligible study population of the AASK Cohort Study consisted of all randomized individuals in the AASK trial who did not reach ESRD by the end of the trial. Participants were eligible for the trial if they were self-identified African Americans, aged 18 to 70 years, with hypertensive CKD as defined by a diastolic BP higher than 95 mm Hg and a GFR between 20 mL/min/1.73 m² and 65 mL/min/1.73 m².

Outcome

African Americans with hypertensive CKD who were treated with currently recommended BP therapy (drugs and level of blood pressure continued to progress during the long-term.