African Americans with hypertensive nephrosclerosis (chronic kidney
disease [CKD] caused by high blood pressure [BP]) have a higher risk
of progressing to end-stage renal disease (ESRD) than of dying from
a cardiovascular event. This was the conclusion of a study presented
here at Renal Week 2008, the American Society of Nephrology Annual
Meeting.

The study looked at participants from the original African American
Study of Kidney Disease (AASK) Trial (1996¡V2001), which had a
randomized 3¡Ñ2 factorial design and 2 BP groups, and the subsequent
prospective AASK Cohort Study (2002¡V2007), in which the BP goal was
less than 130/80 mm Hg. Of the 1094 eligible patients from the
original AASK trial, 691 (63.1%) were enrolled in the subsequent
AASK Cohort Study. The patients received intensive follow-up to keep
their BP at the target level.

"In the cohort study, we used a number of medications to control
BP," lead investigator Tahira Alves, MD, from Vanderbilt University
in Nashville, Tennessee, told Medscape Nephrology. "Our first tier
of medications [was angiotensin-converting-enzyme inhibitors] or
[angiotensin-receptor blockers], then beta blockers or diuretics. We
only used calcium-channel blockers as a third tier when the first 2
groups of medications failed to achieve target BP. We know that half
of the people with CKD require 3 to 5 medications to control BP; the
average number in the AASK trial was 2.5."

At the start of the original trial, average age was 54.6 years, mean
baseline BP was 150/96 mm Hg, mean serum creatinine level was 1.8
mg/dL, and mean glomerular filtration rate was 46.4 mg/mL/1.73 m2.
Mean BP was 136/82 mm Hg at the start of the cohort study period and
129/74 mm Hg at the end of the cohort study period.

During 11 years of follow-up, patients had a higher risk of
progressing to ESRD than of experiencing cardiovascular events, such
as myocardial infarction. For each 100 patient-years of follow-up,
there were 4 cases of ESRD. By comparison, the rate of
cardiovascular events during the same period was 3.2 per 100 patient-
years.

In addition, the risk for death from cardiovascular disease in the
study was 0.8 per 100 patient-years. Of the 74 deaths that occurred
during the cohort period, more than 60% were from causes other than
cardiovascular disease.

"When you look at the variance in outcomes, compared with the
variance in protocols, we're still writing the results of [the
cohort] study," Dr. Alves told Medscape Nephrology. "The first phase
of the study was specifically targeted to find differences in renal
outcomes; cardiovascular outcomes were secondary. But when we
stratified the groups looking at cardiovascular outcomes by
different BP groups and different BP medications, there was no
significant difference in outcomes."

"In virtually all previous studies of patients with CKD (where the
population was multiracial and primarily Caucasian), all-cause
mortality rates were substantially higher than ESRD rates," Dr.
Alves said in her presentation. "The AASK trial and the subsequent
cohort study allow the medical community to gain a broader
understanding of incident cardiovascular disease and mortality
during long-term follow-up in an entirely African American
population with nondiabetic hypertensive nephrosclerosis."

David C. Wheeler, MD, one of the moderators of the session,
commented that "in most population studies, patients with early
(stage 3 or 4) chronic kidney disease are more likely to die than to
reach end-stage kidney failure. This study of African Americans
showed the opposite," Dr. Wheeler told Medscape Nephrology.

"The study is based on a cohort of selected patients involved in a
randomized controlled trial, which may not be representative of the
population as a whole. The results are unlikely to change practice,
since most clinicians would offer patients with CKD (whatever their
ethnicity) treatments that both slow the progression of kidney
damage and reduce the risk of cardiovascular disease, the major
cause of premature death," Dr. Wheeler explained. He is a reader in
nephrology at University College London Medical School and a member
of the advisory board of the US Kidney Disease Outcomes Quality
Initiative.

However, the results may provide additional insights into the
relation between high BP and kidney disease in African Americans, as
well as some of the reported racial differences in the rates and
outcomes of ESRD, Dr. Alves said.

The AASK studies were supported by the National Institute of
Diabetes and Kidney Diseases, and the National Institutes of Health.
Dr. Alves and Dr. Wheeler have disclosed no relevant financial
relationships.

Renal Week 2008: American Society of Nephrology (ASN) Annual
Meeting: Abstract TH-FC051. Presented November 6, 2008.