(November 30, 2007 - Insidermedicine) High cholesterol clearly increases the risk of having a heart attack caused by a blood clot, but it is far less clear whether it increases the risk of a blood clot in the brain, causing a stroke, according to research published in The Lancet.

Here are some facts about cholesterol:

•    High cholesterol is believed to put you at increased risk of both heart attack and stroke, so it is important to try to keep it under control.

•    You should have your cholesterol checked regularly if you are male and over 40 or female and over 50 or post-menopausal. You should also have it checked if you have a history of heart disease, stroke, diabetes, or high blood pressure; your waist measures more than 102 cm (40 in) for men or 88 cm (35 in) for women; or you have a family history of heart disease or stroke

•    Changing your lifestyle can help keep your cholesterol in check. This includes eating less fat, choosing healthy, unsaturated fats over saturated and trans fats, staying physically active, and not smoking.

Investigators from Oxford University looked at data from 61 studies that explored rates of heart attack and stroke in nearly 900,000 adults, mainly from Western Europe and America.

The authors found that dropping cholesterol levels by as little as 1 mmol/L, an amount that can easily be achieved by taking cholesterol-lowering drugs, can more than halve the risk of having a blood clot-related heart attack in people aged 40 to 49. It also significantly reduces the risk in older adults. Changes in cholesterol level reduced the risk for heart attack by the same amount regardless of the individuals' blood pressure, which is another risk factor for heart attack and stroke.

In contrast, the investigators found little connection between cholesterol level and the risk of having a stroke . While a weak connection was seen between cholesterol and stroke in those aged 40 to 59, this link was largely explained by the fact that people with higher cholesterol also tend to have higher blood pressures.

This research confirms the direct connection between high cholesterol and heart attacks but calls into question the relationship between high cholesterol and stroke. Nevertheless, the authors say there is strong evidence that cholesterol lowering drugs reduce the risk of both heart attack and stroke and should therefore continue to be used to help reduce the risk of both these events.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.