"This was not a randomized trial so we could not demonstrate cause-and-effect," Berger said. "Aspirin was associated with a significant reduction in death, yet we are unable to conclude that aspirin caused the reduction."
Past studies have shown that aspirin can reduce fatal and nonfatal cardiovascular problems in patients with cardiovascular disease. Despite this well known protective effect, less than half of all women in the study took aspirin regularly, Berger said.
"Unfortunately, when you look at the aspirin data, you find that women have been under-represented in many of the studies," he said. "There is no conclusive data that provides the optimal dose or effect of aspirin usage in women."
"That was surprising and disappointing. Many studies have shown that 81 mg is just as effective in the secondary prevention of cardiovascular events as 325 mg. And it is well known that the higher the dose, the more likely you are to suffer side effects. Why so many women were on the higher dose was unclear.
"Whether a woman was taking 81 mg or 325 mg, the reduction in death rate was the same, and that point, I think, is the most noteworthy of the study," Berger said. "It is difficult from this study to say that the 81 mg dose is better than 325 mg, but it does appear that it is as effective as 325 mg."
He also noted that because only postmenopausal women participated in the WHI study, the findings reported today may not apply to young women with CVD.
"We have to do a better job of making sure that women who need aspirin get aspirin," Berger said. "Our study should stimulate physicians to explain the benefits of aspirin to select groups of female patients. For patients who worry about aspirin's side effects, this study shows that the smallest dose necessary is just a baby aspirin a day."