LONDON - A ONCE-a-week pill to treat rheumatoid arthritis significantly reduces the risk of heart attack and stroke for people with the painful joint condition, an international team of researchers said on Thursday.

The findings published in the journal Arthritis & Therapy provides further evidence of the benefits of the generic drug methotrexate and underscores the importance of prescribing it early on, the researchers said.

'This shows that we are really making a difference in patients' lives,' said Tuulikki Sokka, a researcher at Jyvaskyla Central Hospital in Finland, who worked on the study.

About 20 million people worldwide have rheumatoid arthritis, an autoimmune disease caused when the body confuses healthy tissue for foreign substances and attacks itself.

Some drugs used to treat it reduce inflammation directly while others tone down immune system response - leaving patients vulnerable to infections and cancer.

Methotrexate was developed as a cancer drug and works by altering the body's use of folic acid, which is needed for cell growth. It may begin to work as early as three to six weeks after treatment starts.

The results are part of a long-term study of more than 4,300 people in 15 countries examining the causes and effects of rheumatoid arthritis and the potential benefits of medications.

The team - which included researchers from Spain, Argentina and the United States - adjusted for traditional risk factors such as exercise, smoking and diabetes and found potential health benefits for people given methotrexate .

Using methotrexate for one year cut the risk of heart attack by 18 per cent and the risk of a stroke by 11 per cent, the researchers said.

Results also suggested that newer drugs that block an inflammatory protein called tumour necrosis factor, or TNF, were also effective at reducing heart attack and stroke risk, although more research is needed, Sokka said.

This class of drugs includes Johnson & Johnson's Remicade, Amgen's Enbrel, and Abbott Laboratories's Humira. The drugs are expensive, which is why people often do not get them right away. -- REUTERS