Ten million to 20 million people in the United States
have chronic kidney disease, but most don't know it,
according to a study by researchers at the Johns Hopkins
Bloomberg School of Public Health, the National Institute
of Diabetes and Digestive and Kidney Diseases at the
National Institutes of Health, and the National Center for
Health Statistics. The findings are published in the
January print edition of the Journal of the American
Society of Nephrology and on the journal's Web site.
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 found that
the number of people with earlier stages of kidney disease
remained stable, with 7.4 million people having less than
half the kidney function of a healthy young adult and
another 11.3 million consistently having protein in their
urine. The researchers can't explain this paradox but
suggest that fewer patients may be dying, and more may be
progressing to dialysis faster.
"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, lead author of the study
and professor of
epidemiology, medicine and
at the Bloomberg
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 noninstitutionalized adults.
In the 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.
Lack of awareness may be due in part to most doctors'
sole reliance on a test that measures the blood level of a
substance called creatinine. Unfortunately, the test is
affected by muscle mass and other person-to-person
variables. "Most blood tests include creatinine, but the
numbers can be misleading. Kidney disease can be quite
advanced before it's found this way," said Thomas H.
Hostetter, senior study author and director of NIDDK's
National Kidney Disease Education Program. NKDEP recommends
that doctors take creatinine a simple step further to
estimate glomerular filtration rate, which is a more
accurate gauge of how well the kidneys are working.
"We can use a patient's creatinine number, age, gender
and race to estimate GFR and find kidney disease earlier,
when there's still time to treat it. A free GFR calculator
makes estimating a snap," Hostetter said. NKDEP is also
working to make the task even easier for busy physicians.
"We are very pleased that several major labs have agreed to
automatically report GFR whenever creatinine is measured.
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
The study was written by Josef Coresh, Danita
Byrd-Holt, Brad C. Astor, Josephine P. Briggs, Paul W.
Eggers, David A. Lacher and Thomas H. Hostetter. Funding
was provided by the National Center for Research Resources
and the National Institute of Diabetes and Digestive and
Kidney Diseases at the National Institutes of Health, and
by the American Heart Association Established Investigators