NEW YORK, Mar 25 (Reuters) Studies have suggested that aspirin is less effective for preventing heart attack in women than in men, although women do benefit from a similar reduction in risk of stroke due to a blocked artery. However, a new study shows that the apparent lower efficacy in women is not due to a failure of aspirin to reduce platelet clumping or aggregation, as has been proposed.

''Women are clearly benefiting from taking aspirin and should continue to take it to improve their cardiovascular health,'' Dr.

Diane M. Becker states in a Johns Hopkins press release. ''Aspirin has been proven by all previous studies to lower the risk of stroke and, as our latest findings show, it also reduces platelet aggregation that can lead to potentially fatal clots in blood vessels.'' To explore why aspirin seems to exert different effects in men and women, Becker, from the Johns Hopkins Medical Institutions in Baltimore, and her team studied the effects of 14 days of aspirin therapy on platelets -- elements in the blood involved in clotting.

Included in the study were the apparently healthy siblings of 403 patients who developed heart disease events before 60 years of age, along with their adult offspring (571 men, 711 women).

The findings are reported in the Journal of the American Medical Association.

The team observed in both men and women that aspirin, taken daily for a two-week period, blocks key biological pathways that lead to platelet clumping. Using an electrical measure of how well platelets stick together, researchers found that clumping decreased similarly in aspirin-treated men and women.

''Our results show that aspirin does what it is supposed to do in both men and women,'' said platelet biologist and study co-author Dr. Nauder Faraday from Johns Hopkins.

Reuters DH DB0754