Few Americans Are Aware They Have Chronic Kidney Disease
Ten to 20 million people in the United States have kidney disease
but most don't know it, according to researchers at the National
Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
at the National Institutes of Health, the Johns Hopkins Bloomberg
School of Public Health, and the National Center for Health Statistics
(NCHS) at the Centers for Disease Control and Prevention. The findings
are in the Journal of the American Society of Nephrology.
Over the past decade the number of people with kidney failure doubled
and the number starting dialysis or having a first kidney transplant
increased by 50 percent, so that more than 400,000 Americans are
now being treated for kidney failure at a cost of $25 billion annually.
In contrast to these dramatic increases, the study also found that
the number of people with earlier stages of kidney disease remained
stable. About 7.4 million people have less than half the kidney
function of a healthy young adult. Another 11.3 million have at
least half of what's considered normal function, but they also have
persistent protein in their urine, a sign of kidney disease. The
researchers can't explain the paradox between stable prevalence
of kidney disease and rising incidence of kidney failure, but they
suggest that fewer patients may be dying and more may be progressing
faster to dialysis.
"Given the high prevalence of chronic kidney disease, we need
to increase awareness, diagnosis and treatment if we are going to
reduce the rate of progression and complications. Most critical
are control of diabetes and hypertension," said Josef Coresh,
M.D., Ph.D., lead author of the study and professor of epidemiology,
medicine and biostatistics at the Bloomberg School of Public Health
Coresh and his colleagues estimated awareness of chronic kidney
disease among 4,101 people in the United States from 1999 to 2000
and compared disease prevalence in those years with that from 1988
to 1994, when 15,488 people were surveyed. Data were from two National
Health and Nutrition Examination Surveys by NCHS of nationally representative,
In the most recent survey, participants were asked: "Have you
ever been told by a doctor or other health professional that you
had weak or failing kidneys (excluding kidney stones, bladder infections,
or incontinence)?" Less than 10 percent of adults with moderately
decreased kidney function (one half to one quarter the filtering
capacity of a young healthy adult) reported being told they had
weakened or failing kidneys. Awareness was low in all but the most
severe stages of kidney disease. Women with moderately decreased
kidney function were significantly less aware of their illness compared
to similarly affected men. The researchers determined actual kidney
function from blood and urine tests and estimated glomerular filtration
rate (GFR), a measure of how well the kidneys are filtering waste
from the blood.
Lack of awareness may be due in part to doctors' sole reliance
on the blood level of a substance known as creatinine. Because muscle
mass and other person-to-person variables can alter creatinine levels,
a "normal" reading can provide a false sense of security.
Instead, creatinine should be considered along with a patient's
age, gender, and race to estimate GFR.
"Kidney disease can be well advanced before it's found with
creatinine alone. GFR is a more accurate gauge of how well the kidneys
work, and our free calculator makes finding the rate a snap,"
said Thomas H. Hostetter, M.D., senior author of the study and director
of NIDDK's National Kidney Disease Education Program (NKDEP). "The
earlier we identify kidney disease the sooner we can treat it,"
NKDEP is asking labs to streamline the process for identifying
kidney disease. "The GFR calculator is a great tool, but it's
still one more step for busy doctors' offices. We are really pleased
that several major labs have agreed to automatically report estimated
GFR whenever creatinine is measured, removing a potential barrier
to finding kidney disease early," said Hostetter. "We
are still working quite hard to standardize tests for kidney disease
by all labs."
People with chronic kidney disease are at high risk for premature
death, heart attacks and strokes as well as hypertension, anemia,
bone disease and malnutrition. NKDEP strives to increase awareness
about kidney disease and offers the GFR calculator and other free
tools at www.nkdep.nih.gov.
"Chronic Kidney Disease Awareness, Prevalence and Trends among
U.S. Adults, 1999 to 2000" was written by Josef Coresh, Danita
Byrd-Holt, Brad C. Astor, Josephine P. Briggs, Paul W. Eggers, David
A. Lacher and Thomas H. Hostetter. The paper was published online
on November 24, 2004, and will appear in print January 2004 in the
Journal of the American Society of Nephrology.
Funding for the study was provided by the National Institute of
Diabetes and Digestive and Kidney Diseases and the National Center
for Research Resources at the National Institutes of Health and
by the American Heart Association Established Investigators Award.