Oily Fish Can Protect Against RA, But Smoking And Psychosocial Stress Increase Its Risk

Results from the EIRA study



New data presented at EULAR 2008, the Annual Congress of the European League Against Rheumatism in Paris, France, show that intake of oily fish is associated with a reduced risk of developing rheumatoid arthritis (RA), whereas psychosocial work stress and smoking can increase the risk of developing the condition. The findings, all taken from a large population-based case-control study in Sweden called EIRA (Epidemiological Investigation of Rheumatoid Arthritis), shed light on the important role of environmental and social factors in the development of RA.



Intake of Oily Fish



For the first time, the intake of oily fish has been demonstrated to have a protective effect against the development of RA, reducing an individual's risk by 20-30%. Studying 1,899 subjects with a confirmed diagnosis of RA (fulfilling ACR criteria) and 2,145 controls (randomly selected and matched for age, sex and residential area), investigators concluded that the odds ratio (OR) for developing RA was 0.8 (0.7-1.0) for those who consumed oily fish 1-7 times per week or 1-3 times per month, compared with those who never, or seldom consumed oily fish. Interestingly, no significant association with RA risk was observed for consumption of fish oil supplements.



Smoking Dosage



Tobacco smoking is an established risk factor for RA, but the investigators found that there is a dose dependency for the level of smoking (i.e. the number of cigarettes smoked across a given period) on the odds ratio of developing anti-citrulline (anti-CCP) positive RA. The highest odds ratios were seen in those carrying a risk variant of the susceptibility gene PTPN22. In the study, 1,240 cases and 798 controls were identified as smokers from a total group of 1,419 cases and 1,674 controls via an extensive questionnaire regarding lifestyle factors, including smoking habits.



These subjects were then classified into three different groups according to the number of pack years smoked - less then 10, 10-20 or more than 20 pack years (where one pack-year is equivalent to having smoked one pack per day for one year) and genotyped to determine the presence of the PTPN22 risk allele.



Psychosocial Stress at Work



Psychosocial stress at work, defined as low decision latitude (or low level of control) was found to be associated with a higher risk for RA. Collected via a validated questionnaire, this was demonstrated in both self-reported data (OR=1.6 (95% CI 1.2-2.2)) and JEM (job exposure matrix)-derived data (OR=1.3 (95% CI 1.0-1.7)). These results were only marginally changed when the investigators adjusted the odds ratios for social class and smoking for the 1,221 cases and 1,454 controls who participated in the study.



Mrs Annmarie Wesley of the Institute of Environmental Medicine, Stockholm, Sweden, EIRA investigator and lead author of the oily fish intake study, commented: "The findings from these studies add to an increasing body of evidence to support the assertion that lifestyle modifications can have a significant impact on an individual's risk for developing RA, one of the most common autoimmune diseases, affecting approximately 1% of adults worldwide. We hope that the data will contribute to the growing understanding of the aetiology of RA and, ultimately, its treatment and prevention"




















Abstract numbers: FRI0034, FRI0054 and SAT0129AHP



About EULAR
The European League Against Rheumatism (EULAR) is the organisation which represents the patient, health professional and scientific societies of rheumatology of all the European nations.


The aims of EULAR are to reduce the burden of rheumatic diseases on the individual and society and to improve the treatment, prevention and rehabilitation of musculoskeletal diseases. To this end, EULAR fosters excellence in education and research in the field of rheumatology. It promotes the translation of research advances into daily care and fights for the recognition of the needs of people with musculoskeletal diseases by the governing bodies in Europe.


Diseases of bones and joints, such as rheumatoid arthritis and osteoarthritis cause disability in 4 - 5 % of the adult population and are predicted to rise as people live longer.


As new treatments emerge and cellular mechanisms are discovered, EULAR 2008 brings together more than 12,000 experts - scientists, clinicians, healthcare workers, pharmaceutical companies and patients - to share their knowledge in a global endeavour to challenge the pain and disability caused by musculo-skeletal disorders.


To find out more information about the activities of EULAR, visit: eular/

Source: Rory Berrie / Camilla Dormer


European League Against Rheumatism