Risk Factors for painful rheumatoid arthritis
McWilliams DF, Zhang W, Mansell JS, Kiely PDW, Young A, Walsh DA. Predictors of change in bodily pain in early rheumatoid arthritis: the ERAN study. Arthritis Care Research 2012, 64(10), 1505-1513.
Key findings and importance of the study
Rheumatoid arthritis (RA) is a painful, inflammatory condition. The inflammation may often be controlled by medication, but the effects on pain are less certain. By looking at the Early Rheumatoid Arthritis Network (ERAN) cohort study we estimated which people were prone to experience more pain and feel worse at diagnosis. This will be used to help inform further research into the causes of pain which may be important for people suffering with RA.
Rheumatoid Arthritis affects 400,000 people in the UK alone and whilst the inflammation may be controlled by medication, it is less easy to know how this affects the pain associated with the disease and how the pain is experienced differently in men and women.
Aim of the study
We looked at information taken from people with new RA to see if we could link people’s different characteristics to changes in pain over one year.
How the study was carried out
We looked at a research database from the Early Rheumatoid Arthritis Network (ERAN) cohort study. This database contained measurements and information from more than 1100 people. The study participants were recruited from 22 different hospitals in the UK and Eire, and all gave permission for their information to be used for research that followed their progress through the years. Our analysis was performed to take into account the influence of other factors on pain that might confound or bias the study.
What the study found
We found that worse than average pain was experienced by men at the time of diagnosis, but that women improved less and had more pain after one year of treatment. Other studies have also found that men and women report their pain differently in a variety of conditions.
We also estimated which people were likely to experience more pain and to feel worse at the time of their diagnosis of RA. This was done by calculating an index called DAS28-P. People with above average DAS28-P were likely to have more pain after one year.
Finally, we also found that people who were experiencing more pain at the time of RA diagnosis were likely to improve more after one year. This seems to be because they had more scope for improvement but might possibly be because they received more medical attention.
Other factors, including well-known measures of RA, and established drugs treatments did not have much value for predicting pain in our study. This is surprising, and shows that the changes in RA pain are difficult to predict.
Significance of the study to Pain Centre’s research
The DAS28-P index will be used for further research about causes of pain that work separately to joint swelling and inflammation, and may be important for some people with RA.