A worrying new study has found that taking some commonly prescribed painkillers for even a short while might increase the risk of dying from a heart attack or stroke in heart attack survivors.

The study found that when heart attack survivors took the drugs for as little as a week, it appeared to boost their risk of another heart attack, stroke or sudden death.

The results, published in Circulation, a journal of the American Heart Association, surprised even the researchers.

Scientists in Denmark were tracking over 83,000 patients who were recovering from heart attacks and prescribed a painkiller type called an NSAID, or a non-steroidal anti-inflammatory.

This class of drugs includes such prescription medications as diclofenac, as well as over-the-counter drugs like ibuprofen, sometimes sold as Advil, and naproxen, sold as Aleve.

While previous research has found risks with the long-term use of NSAIDs in patients with heart problems, researchers expected to find short-term use to be safe overall. They were wrong.

Taking an NSAID was linked to a 45 per cent increased risk of death or recurrent heart attack within as little as one week of treatment. That risk rose to a 55 per cent increased risk if the patients took the drugs for as long as three months.

The researchers note that the study was observational, not a controlled study, so it's not certain the medications were responsible for the increased risk they observed.

Of the nearly 83,700 heart attack survivors studied, most -- 63 per cent -- were men, and their average age was 68. A little less than half (42.3 per cent) had a least one prescription for an NSAID.

The most common NSAIDs prescribed were ibuprofen (23 per cent) and diclofenac (13.4 per cent). Another 4.8 per cent were taking Celebrex (celecoxib), while 4.7 per cent were taking the now-discontinued Vioxx (rofecoxib).

All the drugs were associated with an increased risk of death or recurrent heart attack. Diclofenac had the highest risk -- nearly three times the risk.

Naproxen was not associated with an increased risk of death or recurrent heart attack; however, previous studies have found an increased gastrointestinal bleeding risk with naproxen.

It's not clear why NSAIDs might be linked to increased risks in those with previous heart problems. Doctors think the drugs might boost blood pressure, promote clots, or possibly trigger kidney problems.

The study authors say their findings suggest "there is no apparent safe therapeutic window for NSAIDs in patients with prior heart attack."

They also say many physicians may not be aware that the risk from these drugs might kick in early.

"It is a huge problem. These drugs are very commonly used and not all physicians are aware," principal investigator Dr. Gunnar Gislason of Copenhagen University Hospital told CTV News. "It is a big problem and I hope we get message out to doctors."

Gislason also notes that heart disease patients or heart attack survivors should not be regularly using painkillers without consulting with their doctor.

The results surprised Canadian heart specialist Dr. Michel Le May of the University of Ottawa Heart Institute.

"People think these NSAIDS are safe if they are given over a short course just to get over the illness, but even a short course may be associated with an increased risk of dying," he notes.

Recently, the U.S. Food and Drug Administration issued a warning that diclofenac should not be used by patients recovering from heart surgery. But "the accumulating evidence suggests that we must limit NSAID use to the absolute minimum in patients with established cardiovascular disease," the researchers said.

Further study is warranted, the authors say, to establish the heart safety of NSAIDs.

With a report from CTV medical specialist Avis Favaro