OP0045 SMOKING AND SOCIO-ECONOMIC INDEX ARE INDEPENDENT PREDICTORS OF RHEUMATOID ARTHRITIS
U. Bergström 1,*L. T. Jacobsson 1J.-Å. N. Nilsson 1G. Berglund 2C. Turesson 1
1Rheumatology, Skåne University Hospital, 2Clinical Sciences, Malmö, Lund University, Malmö, Sweden
Background: Suggested risk factors for the development of rheumatoid arthritis (RA) include genetic factors and environmental factors, which both are of potential interest for both prevention and treatment of RA. Smoking and low level of education have been associated with RA, but the underlying mechanisms are unknown. Level of education is known to be closely related with subsequent socio-economic status, which can be measured using the socio-economic index.
Objectives: The purpose of this study was to examine the effect of smoking and socio-economic index on the future risk of RA.
Methods: Between 1974 and 1992, subjects (n=33346; 22444 men and 10902 women) from a defined catchment area were included in a Preventive Medicine Program (PMP). Information on life style factors was obtained using a self administered questionnaire.
Classification of socio-economic index was based on information on job title, tasks and position at work. The procedure was adapted from the one used in the 1989 Swedish population census (National Bureau of Statistics, Sweden, 1989). In the present study, the socio-economic index information was collapsed into two predefined categories, white-collar workers and blue-collar workers. Retired individuals were classified according to position before retirement. Housewives, students, unemployed, self-employed and farmers were excluded. From this population, we have identified individuals who developed RA after inclusion, by linking the PMP register to our local RA register, the local patient administrative register, the National Hospital Discharge Register and the National Cause of Death Register. In a structured review of the medical records, patients were classified according to the 1987 American College of Rheumatology (ACR) criteria for RA, and the year of RA diagnosis was noted. Four controls for every case, matched for sex, year of birth and year of screening, who were alive and free of RA when the index person was diagnosed with RA, were selected from the PMP register. The impact of potential predictors of RA was examined in conditional logistic regression.
Results: Two hundred and ninety six patients (153 men and 143 women) were diagnosed with RA and fulfilled the ACR criteria after inclusion in the PMP. The median time from inclusion to RA diagnosis was 12 years (interquartile range 8–18). Mean age at diagnosis was 60 years. Current smoking at inclusion predicted RA [odds ratio (OR) 1.55; 95 % confidence interval (CI) 1.20 to 2.01] with a similar effect for men and women. Blue-collar workers had an increased risk of RA compared to white-collar workers (OR 1.41; CI 1.02 to 1.94). In multivariate models, the association between RA and smoking (OR 1.95; CI 1.39 to 2.76) and blue-collar work (OR 1.53; CI 1.12 to 2.10) remained significant.
Conclusion: Smoking is a significant risk factor for RA in men as well as in women. Smoking and socio-economic index are independent risk factors for developing RA. This suggests that several different exposures related to socio-economic status are important for RA susceptibility. The role of socio-economic factors in RA development and progression should be further studied.
Disclosure of Interest: None declared