THURSDAY, July 22 (HealthDay News) -- People with extremely low
levels of "bad" cholesterol as a result of taking statins don't
seem to benefit from increased levels of "good" cholesterol, a new
study suggests.
The conventional wisdom has been that to reduce the risk of
heart attack and stroke you should lower your LDL, or "bad,"
cholesterol and increase your HDL, or "good," cholesterol. But
researchers made a surprising discovery: for those with rock-bottom
levels of LDL cholesterol induced by high-dose statin therapy, high
HDL levels don't seem to matter.
Statins include widely used medications such as Crestor, Lipitor
and Zocor.
For people not taking a statin (in the case of this study,
Crestor), high concentrations of good cholesterol still offered
heart protection, the researchers found.
"HDL cholesterol is a well-established 'protective risk factor' for heart disease, which has lead to speculation that drugs capable of increasing HDL cholesterol might be beneficial," said lead researcher Dr. Paul Ridker, the Eugene Braunwald Professor of Medicine at Harvard Medical School and director of the Center for Cardiovascular Disease Prevention at Brigham and Women's Hospital in Boston.
However, most of that data comes from studies of patients in the
West with high levels of LDL cholesterol, he said. "In this work,
we wanted to know if HDL cholesterol levels remain an important
predictor of risk when we dropped LDL cholesterol down to very low
ranges rarely seen in the West," he said.
The report on the randomized, double-blind trial is published in
the July 22 online edition of
The Lancet.
For the study, Ridker's team used data from the JUPITER trial,
in which people with average to low levels of bad cholesterol were
given 20 milligrams of rosuvastatin (Crestor) daily.
In many patients, the drug reduced LDL cholesterol levels to the
low levels seen among Aboriginal populations, but not usually seen
among people in developed countries, the researchers noted.
During a follow-up of up to five years, people taking Crestor
had a 54 percent reduction in heart attack and 48 percent decrease
in stroke.
In addition, people taking Crestor had a 46 percent reduction in
revascularization (surgery to restore an adequate blood supply to
part of the body through a blood vessel graft, like a coronary
bypass) and a 43 percent decrease in venous thromboembolism (a
blood clot in the leg). There was also a 20 percent decrease in
total mortality.
However, when the researchers looked at the effect of "good"
cholesterol on reducing the risk of heart attack and stroke, they
found no significant relationship between levels of good
cholesterol and cardiovascular risk among people taking
Crestor.
Among people in the trial given a placebo, levels of good
cholesterol remained predictive of cardiovascular risk. Among
people with the highest levels of HDL cholesterol, the risk of
heart attack or stroke was about half that of those with the lowest
HDL levels, Ridker's group found.
"One of the implications of this work is to rethink just how important HDL cholesterol remains once we get LDL levels very low with potent statin therapy," Ridker said. "Clinically, these data suggest that once on a high-dose statin, it is unclear if HDL cholesterol remains an important determinant of residual risk."
"These data do not diminish our need to find out once and for all whether potent HDL-raising agents might improve cardiovascular outcomes," Ridker said. The researchers said that further clincial trials were needed to make that determination.
The JUPITER trial was funded by the pharmaceutical giant
AstraZeneca, the maker of Crestor.
Dr. Gregg C. Fonarow, director of the Ahmanson-UCLA
Cardiomyopathy Center at the University of California, Los Angeles,
said that "while statin therapy lowers the risk of cardiovascular
events by 25 to 50 percent, it has been speculated that low HDL
cholesterol levels may account for a large component of the
residual vascular risk that remains despite statin therapy."
In the cases of primary prevention patients treated with
statins, this latest finding challenges that hypothesis, Fonarow
said.
"The most evidence-based and effective approach to reduce the risk of heart attack and stroke is lowering LDL cholesterol with maximally tolerated doses of statin therapy, along with lifestyle modification, even in the setting of low HDL," he said.
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