High Blood
Triglycerides are Independent Risk Factor for Stroke
DALLAS, Dec. 11 - For the first time, researchers have shown that high triglycerides
- a type of blood fat - are a strong independent predictor of a person's risk
for stroke, according to a report in today's Circulation: Journal of the American
Heart Association. "High triglycerides are associated with ischemic stroke
and transient ischemic
attacks (TIA)," says David Tanne, M.D., lead author of the study. "To
the best of our knowledge, this study is the first to indicate that high triglycerides
expose heart disease patients to increased risk for stroke beyond cholesterol."
In light of this finding, healthcare providers should include triglycerides
as part of their global risk assessment for stroke in all individuals
and know that people can have elevated triglycerides even if their cholesterol
is normal, says Tanne, who is director of the stroke unit, department of neurology,
at Sheba Medical Center, Tel Hashomer,
Israel.
"More effective screening and detection of high blood triglycerides and
treatments to modify this stroke risk factor could further reduce the health
burdens of stroke," says Tanne.
Stroke is the third-largest cause of death in the United States after coronary
heart disease and all forms of cancer. It is a leading cause of serious, long-term
disability in the United States. The most common type of stroke, accounting
for about 80 percent of all cases, is ischemic stroke, which is caused by interruption
of the blood supply to the brain.
Major risk factors for stroke include heredity, smoking, increasing age, high
blood pressure, diabetes, heart disease, and sickle cell anemia. High blood
cholesterol, physical inactivity, obesity and overweight are secondary risk
factors.
For six to eight years, researchers followed 11,177 patients with coronary heart
disease (CHD) but no history of stroke or TIA. Medical histories were obtained
and blood lipids assessed. Participants were 40 to 74 years old, and 78 percent
were men. Researchers identified 941 individuals with cerebrovascular disease,
of whom 487 had ischemic stroke or TIA. A TIA is a "mini-stroke" that
produces stroke-like symptoms but no lasting damage.
Individuals who had a stroke or TIA had higher than average levels of triglycerides
and lower levels of HDL cholesterol. About one-fourth of individuals in the
study had triglyceride levels of 200 mg/dL or higher, a level that increased
their risk for stroke by nearly 30 percent. The increased risk associated with
high triglycerides was found across subgroups of age, gender, patient characteristics
and cholesterol.
Tanne's group conducted the study to shed light on the links among blood lipids
and, in particular, high blood triglycerides and the risk of ischemic stroke.
Individuals with high triglycerides usually also have high blood pressure, insulin
resistance and obesity - a cluster of abnormalities that is called the metabolic
syndrome or "syndrome X." This research better clarifies the association
between lipids and stroke because it looks at triglycerides independently in
a large group of patients, says Tanne.
"Our main finding in this study is that elevated blood triglycerides increase
a person's risk of suffering an ischemic stroke," Tanne says. "Those
with high blood triglycerides (over 200 mg/dL) have a nearly 30 percent higher
risk of suffering a stroke, after taking into account other risk factors for
stroke such as high blood pressure, cigarette smoking or diabetes."
A secondary finding was that individuals with high HDL (high density lipoprotein,
the good cholesterol) were less likely to have a stroke. Triglycerides are found
in fats. Excess levels of triglycerides increase concentrations of two types
of fat particles: chylomicrons and very-low-density lipoproteins. These fat
particles may contribute to the
fatty deposits that obstruct blood flow, increasing the risk for ischemic stroke,
says Tanne.
Triglyceride levels are measured by a standard cholesterol blood test.
The link between triglycerides and stroke is still under investigation, says
Tanne. "However, in addition to the direct atherogenic effect of triglycerides,
these lipids appear to be a marker of a series of other changes that could worsen
atherosclerosis or cause blood clots. High triglycerides are associated with
several abnormalities of the body's
clotting systems, which may contribute further to their association with cardiovascular
disease."
Further studies are required to see if a similar link between blood triglycerides
and stroke exists in individuals without heart disease. If so, specific drugs
or drug combinations for lowering blood lipids may need to be used to prevent
strokes among those with high blood triglycerides, says Tanne.
The American Heart Association recommends the following triglycerides guidelines:
Normal range is less than 150 mg/dL; borderline-high is 150 to 199 mg/dL; high
is 200 to 499 mg/dL; and very high is 500 mg/dL or higher. Following a low-fat
diet, exercising and treating overweight can lower triglyceride levels.