Asthma and inflammatory bowel disease (IBD) are common inflammatory diseases. The aim of this study was to investigate the associations of IBD with asthma and respiratory symptoms.

This study is based on 13,499 participants from seven northern European countries that filled in a postal questionnaire on asthma, respiratory symptoms, IBD including ulcerative colitis and Crohn's disease and various lifestyle variables.

There were 195 participants with IBD. The prevalence of asthma (14.5 vs 8.1%, p = 0.001), different respiratory symptoms (range 11.9–36.8% vs range 6.0–18.6%, p < 0.005), non-infectious rhinitis (52.1 vs. 41.6%, p = 0.004) and chronic rhinosinusitis (11.6 vs 6.0%, p = 0.001) were higher in subjects with IBD than in those without IBD. In multivariable regression analysis, the association between IBD and asthma was statistically significant (OR 1.95 (95% CI 1.28–2.96)) after adjusting for confounders such as sex, BMI, smoking history, educational level and physical activity. There was a significant association between asthma and ulcerative colitis (adjusted OR 2.02 (95% CI 1.27–2.19)), and asthma but not Crohn's disease (adjusted OR 1.66 (95% CI 0.69–3.95)). A significant gender interaction was found with a significant association between IBD and asthma in women but not in men ((OR 2.72 (95% CI 1.67–4.46) vs OR 0.87 (95% CI 0.35–2.19), p = 0.038).

Patients with IBD, particularly those with ulcerative colitis and female, have a higher prevalence of asthma and respiratory symptoms. Our findings indicate that it is important to consider respiratory symptoms and disorders when examining patients with manifest or suspected IBD.