Study ties bone drug to heart problem

Fosamax, a bone-strengthening drug taken by millions of Americans to ward off osteoporosis, appears to nearly double the risk of a potentially serious heart problem in women, according to research by Seattle investigators.

The study compared the histories of nearly 1,700 elderly women who were patients at Seattle's Group Health Cooperative and found that Fosamax significantly raised the odds of developing atrial fibrillation, which can result in rapid and irregular heartbeat that can create clots and lead to strokes, or cause shortness of breath or a feeling of fatigue.

The conclusion follows two other studies last year that unexpectedly found a similar link between osteoporosis drugs and irregular heartbeats.

The latest research likely will add a dose of caution for doctors and patients, particularly those who are at relatively low risk of bone fracture but are at high risk of diabetes or cardiovascular problems.

"This is going to be an important study for physicians to be aware of," said Dr. Philip Mease, an osteoporosis expert at Swedish Medical Center and a clinical professor of rheumatology at the University of Washington. Mease was not involved with the study.

Yet at the same time, Mease stressed that the study on Fosamax, which is generically known as alendronate, turned up only an association — not proof — that it causes atrial fibrillation. Mease warned patients taking Fosamax not to quit on their own.

"I'm concerned about the news leading to mass cessation" of the drug, Mease said, because it could lead to an increase in deaths from bone fractures.

To reach their conclusions, researchers compared the records of 719 women who had been diagnosed with atrial fibrillation at Group Health between 2001 and 2004 against those of 966 women who had never had the condition.

Among the atrial-fibrillation patients, 6.5 percent had taken Fosamax, compared with 4.1 percent in the other group. Researchers calculated that women who had taken Fosamax were 86 percent more likely to have atrial fibrillation than if they had never taken it.

And Fosamax users who were diabetic or taking statins to lower cholesterol were among the most likely to develop irregular heartbeat.

"This adds to the evidence that there may in fact be an association" between the two, said Dr. Susan Heckbert, the study's first author and a professor of epidemiology at UW.

The paper examined only Fosamax, the world's top-selling osteoporosis drug and the preferred brand for Group Health members. It did not compare other bone-strengthening drugs in the same class, which include Actonel, Aredia and Zometa. Mease, the UW physician, said the drugs are about equally effective in preventing fractures.

The paper appeared Monday in the Archives of Internal Medicine. The National Heart, Lung and Blood Institute paid for the study.

Last year, a paper in The New England Journal of Medicine reported that patients given Zometa, which is injected once a year, were more than twice as likely to develop serious atrial fibrillation compared with those given a placebo. That was followed by another report linking Fosamax to heart problems, although the results in that study could have been due to mere chance.

Heckbert said her new research may be enough to make doctors reconsider Fosamax prescriptions for patients who are most vulnerable to heart problems.

"We have a good drug that is very effective at preventing fractures," said Heckbert, who also is an affiliate investigator at Group Health Center for Health Studies. But for patients who aren't at high risk of fractures, "they and their physicians would have to carefully weigh the risks."

About 44 million Americans suffer from osteoporosis, women more than men. After age 50, one in two women will break a bone as a result of osteoporosis. But the risks climb dramatically with age, particularly after 80, according to a Surgeon General's report in 2004.

Half of the Group Health atrial-fibrillation patients were older than 75 and half of the women in the comparison group were over 71.

The risk of atrial fibrillation also increases with age. Three to five percent of people over 65 have it, and almost 9 percent of people over 80.

Mease, the osteoporosis expert, cautions that the research appears to be a solid observational study but falls short of definitely implicating Fosamax.

Mease said osteoporosis remains undertreated among many people at high risk, and it can be lethal: About a quarter of Americans who fracture a hip, for instance, die within a year. Others end up bedridden or in nursing homes.

Still, Mease said he intends to heed the latest warning about Fosamax's potential adverse effect.

"I am going to read [the study] carefully, and probably give my patients a copy of the article," he said.

Kyung Song: 206-464-2423 or ksong@seattletimes.com