A team from the Institute for Prevention of Cardiovascular Disease in Boston are the first to carry out a large scale study of the link between cocaine and heart disease.

They report the findings of their research in the American Heart Association journal Circulation.

Researcher Dr Murray Mittleman said: "Cocaine significantly increases the risk of heart attack in individuals who are otherwise at low risk."

The average age of people in the study who suffered heart attacks soon after using cocaine was only 44 - approximately 17 years younger than the average heart attack patient.

Of the 38 cocaine users who had heart attacks, 29 had no prior symptoms of heart disease.

Major study

Known as the Determinants of Myocardial Infarction Onset Study, the research was carried out between 1989 and 1996 at 64 medical US centres.

It included interviews with 2,664 men and 1,282 women who had suffered a non-fatal heart attack.

Thirty-eight individuals reported cocaine use in the prior year, and nine reported use of the drug within 60 minutes before their heart attacks.

The researchers found that cocaine users are more likely to be male and to smoke cigarettes. Smoking is a major risk factor for heart attack.

Dr Mittleman said: "More research is definitely needed. We would like to learn more about the difference that gender and frequency of use may make in cocaine-associated risk."

The researchers plan a similar study to examine the relationship between stroke and cocaine.

Dr Mittleman said: "Studying the mechanisms by which cocaine triggers heart attack may provide insights into how other factors, such as stress, or sudden exertion, may also trigger heart attacks and strokes."

Several theories

There are several theories about how cocaine may trigger a heart attack.

Cocaine can cause a sudden rise in blood pressure, heart rate and contractions of the left ventricle of the heart. These effects can increase the risk of a heart attack.

Cocaine also tightly squeezes, or constricts, the coronary arteries that feed blood to the heart. If the artery constricts, blood flow to the heart and brain can be obstructed, causing a heart attack or stroke.

Dr Mittleman said: "As the public learns more about the huge risk involved in using cocaine, we hope fewer people will want to experiment with this truly dangerous drug.

"In addition, we hope that drug education campaigns may use this information about the magnitude of the heart-disease risk associated with cocaine use to prevent individuals from becoming first-time users."