Reduced incidence and prevalence of atopy in rheumatoid arthritis. Resultsof a case-control study

Objective. To determine the cumulative incidence and the point prevalence o f atopy in patients with rheumatoid arthritis (RA). Patients and methods. A standardized questionnaire was sent to 300 RA patie nts. Questions concerned previous or present characteristics of atopy (hay fever, asthma and constitutive eczema) and RA. RA patients were matched wit h genetically unrelated controls (sister- or brother-in-law, neighbour or f riend). The same questionnaire (except for questions about RA) was sent to the control subjects. In cases of atopy, patients, controls and the treatin g physicians were contacted by a physician to check the validity of the res ponses. Results. Paired responses were obtained in 173 cases. Information about ato py was obtained for 69 other RA patients. The characteristics of RA were si milar for patients who responded and those who did not respond. The frequen cy of atopy was significantly lower in RA patients than in controls, both f or cumulative incidence (RA 7.5%, controls 18.8%; P < 0.01) and point preva lence (RA 3.5%, controls 16.2%; P < 0.0001). The clinical manifestations of atopy stopped before the onset of RA in eight of the 17 RA patients with a n allergic condition, and there was no subsequent relapse. No effect of RA treatment could account for the remission of atopy. Conclusion. These data support the concept that atopy protects against the future development of RA and that the two diseases could counterbalance one another.