But the combination strategy would not work for patients taking indometacin where a significant cardiovascular risk remains even when patients also take aspirin, the study showed.
Using data from a large Californian database, the researchers looked at the MI risks of over 400,000 patients aged 18 and over with a diagnosis of osteoarthritis or rheumatoid arthritis who were treated with either a COX-2 or a non-aspirin NSAID between January 1999 and June 2004.
There were 15,343 cases of MI, 1,233 of which were fatal.
The researchers found that the increased risk of acute MI associated with NSAID or COX-2 treatment was 'completely reversed' in patients taking meloxicam, sulindac and celecoxib, as well as the withdrawn rofecoxib (Vioxx) when there was concomitant use of aspirin.
However, the risk of indometacin remained statistically significant for patients taking aspirin, and aspirin use had no effect on ibuprofen users' risks.
The researchers acknowledged that a combination of an NSAID or COX-2 selective agent plus aspirin may increase non-cardiovascular risks.
Lead researcher Professor Gurkipal Singh, of the University of Stanford in California, said: 'The potentially increased GI toxicity of the aspirin-NSAID combination needs further evaluation.'
Dr Andrew Moore, director of the Pain Research Institute at the University of Oxford, said: 'Low-dose aspirin is likely to bump up the GI risk.
'You could co-prescribe a proton pump inhibitor (PPI) but compliance is poor. If patients do take PPIs long-term, there is an increased risk of osteoporosis.'
Dr Julian Nash, consultant rheumatologist at the Royal National Orthopaedic Hospital in Stanmore, north London, said: 'More than a half of patients prescribed PPIs are no longer taking them at the end of a year. GPs may think their patients are protected from GI risk when they are not.'
A second study presented at the conference identified the highest risk of acute MI for naproxen and indometacin, with lower risks for ibuprofen and piroxicam.
- EULAR 2006