WASHINGTON (Reuters) - Researchers aiming to establish whether high cholesterol raises the risk of stroke said on Thursday they were baffled by findings indicating lower cholesterol levels were not linked to reduced stroke deaths.
They said their analysis of 61 previous studies involving almost 900,000 adults, conducted mostly in western Europe and North America, clearly showed that people with lower total blood cholesterol levels had a lower heart disease death rate.
But the researchers found no relationship between total cholesterol levels and risk of stroke death, especially at older ages and among people with higher blood pressures.
Dr. Sarah Lewington of the University of Oxford in Britain, one of the researchers, stressed that definitive previous research established that drugs called statins, which lower low density lipoprotein cholesterol, also called LDL or “bad cholesterol, substantially reduce stroke risk.
“I think all we can say is that we don’t really understand what’s going on here. And we need to know more about cholesterol and more about stroke sub-types to find out what’s going on,” Lewington said in a telephone interview.
“I don’t think they (the findings) muddy the fact that statins, which lower cholesterol, do lower stroke risk. We don’t want people who are on a statin thinking, ‘Gosh, I must come off this because if my cholesterol gets lower I’m at a higher risk of stroke.’ That’s absolutely not the case.”
Of the people tracked in the study, ages 40 to 89, about 34,000 died of heart disease and 12,000 of a stroke. The study did not discriminate between ischemic stroke, caused by blocked arteries, or hemorrhagic stroke, caused by a burst blood vessel.
Lower total cholesterol was associated with lower death rates from coronary artery disease, also called ischemic heart disease, among men and women of all ages studied, the researchers reported in the Lancet medical journal.
Caused by fatty deposits that clog arteries, coronary artery disease is a leading cause of worldwide death. The deposits build up in the arteries that supply the heart with blood.
Narrowing of the arteries and reduction in blood flow to the heart can lead to heart attack and other conditions.
In a commentary accompanying the study, two experts in France, Drs. Pierre Amarenco and Gabriel Steg of Bichat-Claude Bernard University Hospital in Paris, wrote that a link between cholesterol and stroke risk “probably exists.”
“Because most of the benefit of statins in preventing cardiovascular events can be ascribed to the LDL reduction, it is puzzling that LDL cholesterol is not associated with stroke risk,” they wrote.
They added that “there is good evidence that lowering blood cholesterol with statins reduces stroke risk.”
Editing by Bill Trott