- NASHVILLE, Tenn. -- While off-the-chart cholesterol levels can trigger
strokes, a new study raises the possibility that unusually low amounts
may sometimes cause them as well.
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- High cholesterol is always portrayed
in public health messages as an undivided evil. A study presented Saturday
at the American Heart Association's annual <http://www.canoe.ca/Health9902/Health/heartdisease.html
stroke conference suggests that, in truth, the facts about cholesterol
are a little more complicated, even though on balance low cholesterol is
still far better than high cholesterol.
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- For many years, experts have been convinced
that too much cholesterol, particularly the variety called low-density
lipoprotein, or LDL, increases the risk of heart disease. But the link
between cholesterol and strokes is less clear-cut.
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- The latest study attempted to sort this
out by looking separately at the effects of cholesterol on the two kinds
of strokes -- bleeding strokes and clot strokes.
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- It found that very high cholesterol raises
the risk of <http://www.canoe.ca/Health9902/Health/heartdisease.htmlstrokes
that result from blood clots in the brain. But it also showed that low
cholesterol increases the hazard of the less common but potentially devastating
hemorrhagic strokes that result from burst blood vessels in the brain.
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- The study calculated that the perfect
cholesterol level -- at least, for preventing strokes -- is about 200,
which coincidentally is the target established by the federal government's
National Cholesterol Education Program.
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- "I swear I didn't plan it that way,"
said Dr. David L. Tirschwell of Harborview Medical Center in Seattle.
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- Other experts argued that the study does
not change the overriding public health message. Even if low cholesterol
carries a small risk, they said, the hazard is vastly overshadowed by its
other benefits to the heart and the brain.
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- By preventing heart attacks and clot
strokes, "lowering cholesterol far, far outweighs the potential negatives
of a hemorrhagic stroke," said Dr. Philip B. Gorelick of Rush Presbyterian
St. Luke's Medical Center in Chicago.
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- Heart attacks are the leading cause of
death in the United States, while strokes are No. 3, striking about 600,000
Americans annually. About 80 percent of <http://www.canoe.ca/Health9902/Health/heartdisease.html
strokes -- what doctors call ischemic strokes -- occur when a blood clot
blocks an artery, choking off oxygen and nutrients to a section of the
brain. The rest are hemorrhagic strokes and result from ruptured blood
vessels that flood the brain with blood.
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- Tirschwell studied 587 victims of ischemic
strokes and 137 victims of hemorrhagic strokes and compared them to 3,743
healthy people. Among the findings:
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- * People with cholesterol over 280 were
twice as likely as those at 230, the group's average, to have an ischemic
stroke.
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- * People with cholesterol under 180 had
double the risk of those at 230 for a hemorrhagic stroke.
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- * High cholesterol probably accounts
for 10 percent to 15 percent of ischemic strokes. Low cholesterol is the
cause of perhaps 7 percent of hemorrhagic strokes.
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- "Our data imply that for stroke,
an optimal level may be around 200," Tirschwell said.
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- While no one knows precisely how low
cholesterol might contribute to hemorrhagic stroke, Tirschwell said one
possibility is that cholesterol is needed to keep blood vessels strong
to prevent rupture.
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- Heart association vice president Dr.
Rodman Stark criticized the study for failing to break down people's cholesterol
into the bad LDL and the good HDL, which protects the arteries.
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- "Even if you accept his conclusion
is true, which I don't think was justified, you might still accept a slightly
increased risk of hemorrhagic stroke in order to significantly reduce the
risk of ischemic stroke, which is four-fifths of the stroke burden,"
he said.
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