The risk of autoimmune connective tissue diseases in patients with atopy: A nationwide population-based cohort study.

BACKGROUND: The relationship between autoimmune connective tissue disease (ACTD) and atopy is controversial.
OBJECTIVES: To investigate the risks of ACTDs in patients with atopic triad diseases, including atopic dermatitis, allergic rhinitis, and asthma, by using a nationwide data base.
METHODS: A cohort of 155,311 patients newly diagnosed with atopic dermatitis, allergic rhinitis, or asthma in 2002-2011 was obtained from the Taiwan National Health Insurance Research Database. An age- and sex-matched control group was selected from the same data base. The association between atopy and ACTD was investigated by using Cox proportional hazards regression analyses.
RESULTS: Atopic dermatitis, allergic rhinitis, and asthma were present in 12.1, 78.6, and 26.3%, respectively, of the patients with atopy. The presence of atopic diseases increased the overall risk of ACTDs (incidence rate ratio 1.85 [95% confidence interval {CI}, 1.52-2.25]). The hazard ratio (HR) for ACTDs remained higher after adjusting for age, sex, urbanization level, socioeconomic status, and comorbidities. Individual risks of systemic lupus erythematosus (HR 1.58 [95% CI, 1.06-2.37]), rheumatoid arthritis (HR 1.74 [95% CI, 1.31-2.33]), and Sjögren syndrome (HR 2.49 [95% CI, 1.71-3.63]) were also higher. The coexistence of atopic triad diseases increased the risk of ACTDs from 1.80 (95% CI, 1.48-2.21) for one atopic disease to 3.29 (95% CI, 1.22-8.88) for three atopic diseases.
CONCLUSION: The presence of atopic triad diseases is significantly associated with risks of systemic lupus erythematosus, rheumatoid arthritis, and Sjögren syndrome, and their coexistence exacerbates this risk. To our knowledge, this was the first study that reported an increased risk of Sjögren syndrome among patients with atopy.