Zsa Zsa Weerts

Impact paragraph 267 A Impact paragraph Irritable bowel syndrome is a highly prevalent disorder affecting 5-15% of the population and is associated with a substantial financial and societal burden. The studies described in this thesis contribute to the long-term goal to further optimize IBS treatment. Impact on healthcare providers The results from this thesis are relevant for people involved in the care of patients with IBS such as general practitioners, gastroenterologists, psychologists, and dieticians. Treatment of cardinal IBS symptoms such as abdominal pain is exceptionally challenging. The large randomized controlled trial on the efficacy of peppermint oil in IBS, the PERSUADE study, showed that peppermint oil is a moderately, though most-likely cost- effective treatment. This allows for appropriate positioning of peppermint oil in the therapeutic arsenal and for more informed decision making. Upper GI symptoms may occur as side effects during treatment with peppermint oil. We demonstrated for the first time that belching severity decreases after three weeks of continues peppermint oil treatment. This particular finding can help healthcare providers who prescribed peppermint oil treatment to better inform patients when this highly burdensome but harmless side-effect occurs. Although part of this thesis focused on (GI-)targeted treatment with peppermint oil, we also showed that improvement in GI symptom severity does not necessarily result in an improvement in quality of life in patients with IBS. Furthermore, we showed that a large part of the total healthcare costs in patients with IBS was spent on mental healthcare. Findings like these can inform healthcare providers about the importance of a multidimensional and integrated treatment and will eventually help them in treating IBS patients successfully. Furthermore, results from the different studies described in this thesis are largely applicable to primary care where general practitioners diagnose and see the majority of patients with IBS. The Maastricht IBS Cohort studies included 28-33% of patients recruited from primary care. The PERSUADE study included 57.7% of patients recruited from primary care. This in itself represents the largest of such population examined with regards to peppermint oil efficacy and led to a high applicability of the results to every- day clinical practice.