2001-12-12 11:01:00
News in Science

For the first time, researchers have shown that high triglycerides - a type of blood fat - is a strong independent predictor of a person's risk for stroke.

The research, published in the journal Circulation this week, indicates that triglycerides should be part of global risk assessments for stroke.

"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," said Dr David Tanne, Director of the stroke unit in the Department of Neurology at Sheba Medical Centre, Tel Hashomer, Israel.

The study followed 11,177 patients with coronary heart disease over six to eight years. Participants were 40-74 years old and 78 per cent were men. People with a history of stroke were excluded.

Researchers identified 941 individuals with cerebrovascular disease, of whom 487 had an ischaemic stroke or a transient ischaemic attack.

An ischaemic stroke is one caused by interruption of the blood supply to the brain, and is the most common type of stroke, accounting for about 80 per cent of all cases. A transient ischaemic attack, or 'mini-stroke', produces stroke-like symptoms but no lasting damage.

People who had a stroke or mini-stroke had higher levels of triglycerides than average and lower levels of high-density lipoprotein cholesterol (HDL, or 'good' cholesterol), the researchers found.

About a quarter of the participants had triglyceride levels of 200mg/dL or higher.

"Those [people] have a nearly 30 per cent higher risk of suffering a stroke, after taking into account other risk factors for stroke such as high blood pressure, cigarette smoking or diabetes," said Dr Tanne.

Triglycerides are a type of fat occurring naturally in blood. They are formed from the digestion of fats in food, and are measured by a standard cholesterol blood test.

Excess levels of triglycerides increase concentrations of very-low-density lipoproteins (LDL, or 'bad' cholesterol). These fat particles may contribute to the fatty deposits that obstruct blood flow, increasing risk for ischaemic stroke.

"High triglycerides are associated with several abnormalities of the body's clotting systems, which may contribute further to their association with cardiovascular disease," said Dr Tanne.

A secondary finding was that individuals with high HDL were less likely to have a stroke.

This research better clarifies the association between lipids and stroke because it looks at triglycerides independently in a large group of patients. Individuals with high triglycerides usually also have high blood pressure, insulin resistance, and obesity, so the effects of each factor can be difficult to tease apart in smaller studies.

The major risk factors for stroke are hereditary, smoking, increasing age, high blood pressure, diabetes, heart disease, and sickle cell anaemia. Secondary risk factors include high blood cholesterol, physical inactivity, and being overweight.

According to the National Heart Foundation of Australia, 17 per cent of Australian men and seven per cent of women aged 20 or over have high blood triglyceride levels.

The proportion increases with age, reaching about 25 per cent in men aged 45-49 and women aged 65-69.