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

To determine the cumulative incidence and the point prevalence of atopy in patients with rheumatoid arthritis (RA).

A standardized questionnaire was sent to 300 RA patients. Questions concerned previous or present characteristics of atopy (hay fever, asthma and constitutive eczema) and RA. RA patients were matched with genetically unrelated controls (sister- or brother-in-law, neighbour or friend). The same questionnaire (except for questions about RA) was sent to the control subjects. In cases of atopy, patients, controls and the treating physicians were contacted by a physician to check the validity of the responses.

Paired responses were obtained in 173 cases. Information about atopy was obtained for 69 other RA patients. The characteristics of RA were similar for patients who responded and those who did not respond. The frequency of atopy was significantly lower in RA patients than in controls, both for cumulative incidence (RA 7.5%, controls 18.8%; P: < 0.01) and point prevalence (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 an allergic condition, and there was no subsequent relapse. No effect of RA treatment could account for the remission of atopy.

These data support the concept that atopy protects against the future development of RA and that the two diseases could counterbalance one another.