Respiratory symptoms and pulmonary functional changes in patients with irritable bowel syndrome

Scientific evidence of functional interface between the immune and sensory motor systems of the gut and respiratory systems has been reported. In recent studies excess prevalence of bronchial hyper-responsiveness has been shown among patients with irritable bowel syndrome (IBS). The purpose of our study was to investigate the possible relationship between IBS and asthma.

One hundred thirty-three patients with IBS (108 women, 25 men) and 137 control subjects (105 women, 32 men) were included in this study. Both for IBS and the control group, the mean ages were 41.64+/-9.45 yr and 39.94+/-10.62 yr, respectively. Patients more than 50 yr old, with any organic GI disease, acute respiratory system infection, current or ex-smokers, and patients using drugs affecting smooth muscle and autonomic nervous system were not included in the study. Respiratory symptoms were questioned and pulmonary function tests were performed for every subject.

There were 45 (33.8%) and eight (5.8%) subjects with respiratory symptoms in IBS and control groups, respectively (p < 0.0001). Twenty-one (15.8%) patients from the IBS group and two (1.45%) patients from the control group had the diagnosis of asthma according to history, clinical, and PFT findings. There was no statistical difference between two groups with respect to percentage of forced vital capacity and forced expiratory volume in 1 s-to-forced vital capacity. The difference between the two groups in forced expiratory volume in 1 s, flow after 50% of the vital capacity has been exhaled, peak expiratory flow rate, and maximal mid-expiratory flow rate was statistically significant (p < 0.01).

We found that the prevalence of asthma was more common in the IBS group than in controls. Our finding supports the speculation that asthma and IBS may share common pathophysiological processes.