Introduction
Prior research has established an association between inflammatory bowel disease (IBD) and obstructive lung diseases (OLD), such as asthma, bronchitis, COPD (chronic obstructive pulmonary disease), and bronchiectasis. Studies have suggested that there may be a bidirectional relationship between IBD and OLD, with patients diagnosed with either condition being more likely to develop the other.1 While previous studies have mainly examined the prevalence of this association,2–4 only two incidence studies have been conducted, both of which focused on the risk of IBD in individuals who were already diagnosed with asthma or COPD.5,6 Consequently, there is a need for further investigation to determine the risk of disease development in people with IBD.
Aims & Methods
The aim was twofold: firstly, to determine the likelihood of OLD prior to the onset of IBD; and secondly, to evaluate the risk of OLD after the onset of IBD.
The present study employed data from the Danish National Patient Registry and the Danish National Prescription Registry, from January 1, 1999, to December 31, 2018.7,8 Incident cases of IBD in Denmark from 2003 to 2013 were identified based on relevant International Classification of Diseases, 10th revision (ICD-10) diagnosis codes.9 A matched population without IBD was included for comparison in a 1:10 ratio. Individuals with OLD were identified based on relevant ICD-10 codes or ATC codes (two on different dates within a year). Additionally, a sensitivity analysis was performed using only ICD-10 codes to estimate the risk of obstructive lung disease.
Logistic regression was applied to estimate the prevalence odds ratio for OLD up to four years before IBD diagnosis/index date. Time-to-event analysis (Cox proportional regression) was then used to explore the risk of OLD. In the sensitivity analyses, the time-to-event analysis was repeated based solely on ICD-10 diagnosis codes.
Results
The total study population consisted of 266,618 individuals: 24,238 with IBD and 242,380 without IBD. Individuals with IBD had a 60% higher likelihood (adjusted odds ratio [aOR]: 1.60, 95% CI: 1.53-1.67) of OLD before diagnosis compared to non-IBD individuals, whereas the risk was over 40% higher after IBD diagnosis. A sensitivity analysis confirmed the elevated risk after IBD diagnosis, with a higher adjusted hazard ratio (aHR) of 1.63 (95% CI: 1.53-1.73).
Conclusion
Our findings suggest a significant bidirectional association between IBD and OLD. We demonstrate in an unprecedented nationwide cohort study, an increased risk of OLD among individuals diagnosed with IBD. Further studies concerning the gut-lung axis are warranted to explore the mechanisms underlying this association.
References
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