Associations may exist between asthma, allergies and rheumatoid arthritis, according to a study recently published in Arthritis & Rheumatology. Rheumatoid arthritis does not appear to be associated with passive exposure to smoke.
This case-control study included 1023 individuals with rheumatoid arthritis, 175 of whom had incident rheumatoid arthritis. Participants were treated within a single center and were identified using a combination of self-reporting and 2 diagnostic codes. Biobank questionnaires were used for self-reporting exposures. Proportions were compared using chi-square tests, with continuous variable comparison conducted using Wilcoxon rank-sum tests. The correlations between exposures and rheumatoid arthritis were calculated using adjusted logistic regression models.
There was a significant association between asthma and rheumatoid arthritis among the entire cohort (odds ratio [OR]=1.28, 95% confidence interval [CI], 1.04-1.58), with adjustments for urban environment, allergy status, and exposure to passive smoke, though not among those with incident rheumatoid arthritis (OR=1.17, 95% CI, 0.66-2.06). However, there was a correlation between allergic disease and rheumatoid arthritis among both the full cohort (OR=1.30, 95% CI, 1.12-1.51) and the incident cohort (OR=1.61, 95% CI, 1.11-2.33). This was especially pronounced among those with a history of food allergies (OR=1.38, 95% CI, 1.08-1.75 for the full cohort; OR=1.83, 95% CI, 0.97-3.45 for the incident cohort). Rheumatoid arthritis was not associated with exposure to secondhand smoke either at work or at home, nor was it associated with the age of beginning to smoke (OR=1.03, 95% CI, 1.00-1.06 for the full cohort; OR=1.00, 95% CI, 0.92-1.08 for the incident cohort).
Limitations to this study include the use of a convenience sample and a resulting potential for selection bias, possible recall bias, the use of self-reporting and possible misclassification bias for rheumatoid arthritis, and a lack of data on rheumatoid arthritis autoantibody status for many participants.
The study researchers conclude that “asthma and allergies may be associated with increased risk of developing [rheumatoid arthritis], but passive smoke exposure and age of smoking initiation are not. Future studies investigating the relationship between [rheumatoid arthritis] and early life atopy are needed.”
This study received funding from the Rheumatology Research Foundation Resident Research Preceptorship.
Kronzer VL, Crowson CS, Sparks JA, Vassallo R, Davis JM III. Investigating asthma, allergic disease, passive smoke exposure, and risk of rheumatoid arthritis [published online February 12, 2019]. Arthritis Rheumatol. doi: 10.1002/art.40858