People may be at an increased risk of developing rheumatoid arthritis (RA) if they smoke, are obese or have diabetes, scientists have discovered.

RA is a painful inflammatory condition affecting the body's joints. Some 40,000 people in Ireland have the condition and it can have a major effect on quality of life. The cause is unknown.

Scientists at the University of Manchester decided to look into any potential link between lifestyle factors and the condition. They monitored the progress of over 25,000 people aged between 40 and 79 over a number of years. Almost 200 of these went on to develop RA.

When the scientists compared those who had developed the painful condition and those who had not, they found that obesity, smoking and diabetes all appeared to increase the risk.

Among women, those who had more than two children and who had breastfed for a shorter amount of time also appeared to have a higher risk of developing RA.

However, among both men and women, drinking small amounts of alcohol and being in a higher social class appeared to reduce the risk.

The scientists believe these finding could be used to develop a simple screening tool, which could be used by GPs to identify those at risk.

"The factors we studied give us vital clues to the early events in the process that ends in someone developing RA. They are also simple to ask about and can be used as part of a prevention programme," said lead scientist, Prof Ian Bruce.

Details of these findings are published in the journal, Annals of the Rheumatic Diseases.

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