BLOOD-TRANSFUSION, SMOKING, AND OBESITY AS RISK-FACTORS FOR THE DEVELOPMENT OF RHEUMATOID-ARTHRITIS - RESULTS FROM A PRIMARY CARE-BASED INCIDENT CASE-CONTROL STUDY IN NORFOLK, ENGLAND

Objective. To examine a range of demographic, social, and clinical ris k factors for the development of rheumatoid arthritis (RA). Methods. P opulation-based case-control study in Norfolk, England, involving adul t patients, ages 18-70, with an inflammatory polyarthritis of <12 mont hs' duration who were recruited from the Norfolk Arthritis Register, C ontrols, matched for sex and date of birth, were selected from the pri mary care register of the Norwich Health Authority, Both cases and con trols completed identical self-administered questionnaires, Matched an alysis of the 165 case-control sets was conducted for the whole group and for the subset in which the cases satisfied the 1987 American Coll ege of Rheumatology criteria for RA. Results. The controls were of hig her socioeconomic status than the cases, This was probably due to resp onse bias, Having a body mass index greater than or equal to 30 was as sociated with an adjusted odds ratio (OR) of 3.74 for developing RA (9 5% confidence interval [95% CI] 1.14-12.27), RA was also associated wi th a history of blood transfusion (OR 4.83, 95% CI 1.29-18.07), Even a fter correcting far social class, a history of having ever smoked was associated with a higher risk of developing RA (OR 1.66, 95% CI 0.95-3 .06). There was no difference between cases and controls in previous e xposure to childhood infections, certain surgical procedures, or repro ductive history variables, Conclusion. RA has a number of potential en vironmental triggers, including smoking, obesity, and blood transfusio n.