Continuation of AASK Cohort Study
Background
African Americans are disproportionately afflicted with end-stage kidney failure,
also known as end-stage renal disease (ESRD). Although they constitute approximately
12 percent of the U.S. population, African Americans comprise 32 percent of the
prevalent ESRD population. In African Americans, especially, hypertension is a major
cause of ESRD. The racial disparity is most striking in young African Americans,
ages 25 to 44, who are 20 times more likely than whites of that age group to develop
kidney failure caused by high blood pressure.
Although better management of high blood pressure has led to a decline in the number
of people who develop strokes and heart disease, the number of people developing
kidney failure has increased. In 1990, the NIDDK launched an initiative to investigate
the underlying cause of ESRD and to study mechanisms that could slow progression
of hypertensive kidney disease in African Americans. The clinical trial, African
American Study of Kidney Disease and Hypertension (AASK), was initiated to investigate
whether a specific class of antihypertensive drugs (beta-adrenergic blockers, calcium
channel blockers, or angiotensin converting enzyme inhibitors) and/or the level
of blood pressure (a mean arterial pressure or MAP of 102-107 mm Hg, or a MAP of
92 mm Hg) would influence progression of hypertensive kidney disease in African
Americans.
After a brief period of pilot study (1992-1994), 20 clinical centers and a data-coordinating
center were funded to carry out the full-scale clinical trial in 1994. The twenty-first
clinical center was added in June 1996. As in the pilot clinical trial, all four
historically black medical schools were funded to participate in the full-scale
trial. The centers required nine months to revise the protocol for the full-scale
trial, and participant recruitment and randomization began in April 1995. The intervention
component ended in March 2002, and the primary analysis of the study results concluded
in June 2002.
In 2001, a significant discovery was made in the treatment strategy for slowing
kidney disease caused by hypertension. Angiotensin-converting enzyme (ACE) inhibitors,
compared with calcium channel blockers, were found to slow kidney disease progression
by 36 percent, and they drastically reduced the risk of kidney failure by 48 percent
in patients who had at least one gram of protein in the urine, a sign of kidney
failure. ACE inhibitors have been the preferred treatment for hypertension caused
by diabetes since 1994; however, calcium channel blockers have been particularly
effective in controlling blood pressure in African Americans. The AASK study now
recommends ACE inhibitors to protect the kidneys from the damaging effects of hypertension.
Continuation of AASK Description
The Continuation of AASK Cohort Study was initiated at the conclusion of the AASK
Intervention Study. The primary goal of the Continuation of AASK Cohort Study is
to investigate the environmental, socio-economic, genetic, physiologic, and other
co-morbid factors that influence progression of kidney disease in a well-characterized
cohort of African Americans with hypertensive kidney disease.
The Continuation of AASK Cohort Study will be followed at the clinical centers.
The patients will be provided with the usual clinical care given to all such patients
at the respective centers. Baseline demographic information, selected laboratory
tests, and other studies are being obtained at the initiation of the Continuation
Study. The patients will be seen quarterly at the centers, and some selected studies
done at these visits. Samples will be obtained and stored for additional studies
and analyses at a later date.
The protocol used in the Continuation of AASK Cohort Study is similar to that proposed
for the new Chronic Renal Insufficiency Cohort (CRIC) Study to be initiated by the
middle to late 2002 to permit ultimate integration and comparison of the two data
sets.
Project Officer: Larry Agodoa, M.D., 301-594-7717
Last Updated 2/17/2004
|