Only half of patients at high risk of heart disease are given the right targets for cutting their cholesterol and millions may suffer heart attack or stroke due to doctors' poor advice, scientists said on Thursday.

German researchers said that over 10 years, around 50 to 80 heart attacks, strokes and heart disease-related deaths per 1,000 patients could be averted if all doctors correctly followed guidelines on cholesterol-lowering targets.

"The numbers highlight the enormous health implications ... in our findings," said Heribert Schunkert, who led the study into more than 25,000 patients in Germany.

Drugs called statins, like Pfizer's Lipitor or AstraZeneca's

Crestor, which lower cholesterol and have been credited with preventing millions of heart attacks and strokes, are often prescribed to patients with high heart risk.

But Schunkert, of the University Clinic of Schleswig Holstein in Luebeck, said guidelines on how much cholesterol should be brought down in each type of patient may be too complex. Doctors often failed, especially with women patients, to recognize the risk and set the right goals, he said.

"Efforts should be made to make guidelines simpler and easier to understand and follow, instruments to identify high-risk patients more easily should be developed, and special attention should be paid to women," he wrote in a commentary on the study, which was published in the European Heart Journal.

Heart disease is the number one killer of men and women Europe, the United States and other industrialized nations and high cholesterol in the blood plays a major part in it.

So-called "bad cholesterol," or low-density lipoprotein (LDL) cholesterol is a fatty substance known as a lipid which is carried in the blood on proteins. Reducing high LDL cholesterol levels with drugs, diet and other lifestyle changes is an important step in trying to prevent heart attacks and strokes.

Doctors are generally advised that the higher the patient's heart disease risk, the lower the cholesterol target should be, but levels of risk are sometimes hard to establish.

Schunkert said patients in lower risk groups — who often have no known heart disease but have an accumulation of risk factors — "frequently ... escape the notice of doctors for aggressive cholesterol-lowering treatment."

The study of 25,250 patients and 907 doctors in Germany and found that only 55 percent of male patients and 49 percent of female patients were given correct LDL targets.

Schunkert said similar scenarios were likely to be found in other European countries and around the world and noted that similar data had been reported from Italy.

"The core question involves the perception of patient risk: for example, women are often perceived as having a lower cardiovascular risk ... and this may lead to insufficient treatment," he wrote. "We hope ... our study will remind physicians of the need to observe relevant guidelines to calculate individually every patient's target value, so that they can deliver the best possible care to all their patients."