Unlike the general public, kidney dialysis patients
with higher cholesterol levels die at a lower rate than
those with lower cholesterol levels. Now, a study by
researchers at the John Hopkins
Bloomberg School of Public
Health has determined that the lower mortality rate of
those with higher cholesterol is likely due to the
cholesterol-lowering effects of inflammation and
malnutrition, two serious complications of kidney dialysis,
and not a benefit of high cholesterol. The study is
published in the Jan. 28 edition of the Journal of the
American Medical Association.
"Using multiple blood tests we were able to show that
the majority of dialysis patients have inflammation and/or
malnutrition, and these conditions distort the meaning of
serum cholesterol. This explains why patients with lower
cholesterol have higher mortality," said Josef Coresh, the
study's senior investigator and an associate professor in
the Department of
Epidemiology at the School of Public Health. "We were
able to show that when dialysis patients don't have
inflammation or malnutrition, higher cholesterol predicted
a progressively higher risk of total and cardiovascular
mortality.
"This is important since it undermines the idea that
high cholesterol can be protective in dialysis patients and
emphasizes the importance of cholesterol treatment," Coresh
said.
The study included 823 dialysis patients from 79
clinics in the United States. Inflammation and/or
malnutrition were detected by looking for abnormalities in
any one of three laboratory tests — C-reactive
protein, interleukin-6 or serum albumin — since any
one test can miss patients with abnormalities. Participants
with inflammation or malnutrition had lower cholesterol
levels than those without either condition.
Overall, higher cholesterol was incrementally
associated with lower mortality, a finding that confirms
other studies in dialysis patients and other sick
populations such as smokers and the elderly. This opposite
association from the expected higher mortality at higher
cholesterol has led some physicians to avoid treating high
cholesterol in dialysis patients. However, among patients
without inflammation or malnutrition, higher cholesterol
was strongly associated with higher mortality.
Yongmei Liu, the study's first author and a doctoral
candidate at the School of Public Health, emphasized that
the findings were similar when cardiovascular disease was
the cause of death. Overall and among participants with
inflammation or malnutrition, cholesterol was not strongly
related to cardiovascular mortality risk. However, among
participants without inflammation or malnutrition, a strong
association between higher cholesterol and higher risk was
seen. "The same serum cholesterol means different things
depending on the presence or absence of inflammation," Liu
said. "In dialysis patients, low serum cholesterol may
signal the presence of poor nutritional status or chronic
inflammation. Physicians should look for signs of
inflammation and malnutrition that can be markers of high
risk and distort the meaning of serum cholesterol. These
findings are also relevant for other sick populations such
as older patients and smokers."
According to Coresh, "Cardiovascular disease is a
leading cause of death for patients with kidney failure.
Even though 30 percent of dialysis patients have unhealthy
cholesterol levels, fewer than 10 percent receive any
cholesterol-lowering medication. Our findings show that
this population should be treated for high cholesterol."
The study was written by Yongmei Liu, Josef Coresh,
Joseph A. Eustace, J. Craig Longenecker, Bernard Jaar,
Nancy E. Fink, Russell P. Tracy, Neil R. Powe and Michael
Klag.
It was funded by grants from the National Heart, Lung
and Blood Institute, the National Institute of Diabetes and
Digestive and Kidney Diseases, the American Heart
Association and the National Center for Research
Resources.
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