Stopping aspirin suddenly could be dangerous for heart patients ? a study released on Wednesday shows it can cause a heart attack.

Millions around the world take daily aspirin to reduce their risk of heart attack and stroke. Aspirin helps keep the blood from clotting and may have other beneficial effects on blood vessels.

French researchers said they found 51 patients who had heart attacks or severe ?events? such as unstable angina ? uncontrollable chest pain ? within a week of stopping their aspirin. They told a meeting of the American College of Chest Physicians in Orlando, Florida, that ?aspirin withdrawal? may have been to blame.

?The benefits of aspirin therapy in coronary patients are well known. However, the effects that aspirin withdrawal has on this group of patients are just now being studied,? said Dr Emile Ferrari, of University Hospital Pasteur in Nice, France. ?Our study shows that aspirin therapy cannot be safely stopped in any case, but especially in patients with a history of coronary disease,? Ferrari added in a statement.

They reviewed the cases of 1,236 patients hospitalized for coronary syndromes and found 51 had heart attacks and other severe events less than one week after stopping aspirin.