Study Plan

 

The aim of the EIRA study is to investigate which genetic and environmental factors may cause rheumatoid arthritis. It is one of the first and most ambitious studies of its kind, where the effects of both genes and the environment are assessed. 

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The aetiology of rheumatoid arthritis (RA) is almost unknown, but it is evident that both genes and the environment are involved in the disease development as seen from both concordance data in twins and from a number of epidemiological and genetic studies. While knowledge about the contribution of genetics is rapidly increasing there is still a lack of data on environmental factors which may cause RA.

 

Rheumatoid arthritis (RA) is an autoimmune, inflammatory disease affecting the joints in a symmetrical pattern. Left untreated, the disease causes severe functional disabilities and permanent joint destruction. In addition to physical and social suffering, RA also implies a reduced life expectancy and an increased mortality from cardiovascular diseases, infections and respiratory diseases.

 

Rheumatoid arthritis (RA) occurs worldwide and is more common among women than men. Approximately 23 million people (16.5 million women and 6.5 million men) were suffering from RA in 2002. There seem to be geographical differences in the prevalence of RA, with prevalence estimates of 0.5-1.0% in North America and in northern Europe, but with lower prevalence noted in southern Europe and in some developing countries. Knowledge about RA incidence is limited; however, several Scandinavian countries have reported annual incidence rates of 24-36 cases/100 000 person-years.

 

EIRA is a population-based case-control study. Patients, aged 18-70 years, living in the southern and middle parts of Sweden with newly diagnosed rheumatoid arthritis are included in the study. They are compared with randomly selected control individuals of the same age and sex. All participants answer an extensive questionnaire covering a wide spectrum of issues e.g. smoking, occupational history, exposures of the working environment, alcohol, psychosocial environment and disease history. A blood sample is also taken for genetic analyses.

 

The data collection started in 1996 and is still in progress. To date, 3500 cases and 5350 controls have participated in the study.