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Chapter 9 220 treatment group). A repeated measures ANOVA was performed to assess the influence of time (weeks) on adherence. If the Mauchly’s test indicated that the sphericity assumption was not met, the Greenhouse-Geisser corrected results were reported. A two-sided P <0.050 (2-sided) was considered statistically significant. Results Overall, 190 patients were randomized. One patient was randomized erroneously, i.e. without fulfilling all inclusion criteria. Therefore, 189 patients were analyzed ( N =64 in the placebo group, N =62 in the small intestinal release peppermint group, N =63 in the ileocolonic release peppermint oil group: mean (SD) age 34.0 (13.3) years, 77.8% female, 95.8% Caucasian, 57.7% primary care). Eleven patients withdrew from the study during the treatment period (data until discontinuation were included in the analyses). Baseline characteristics are presented in Table 9.1 . During recruitment, only a single patient stated the digital data-collection as a reason not to participate. Patients’ adherence to the digital symptom diary Most patients used their own smartphones, but four out of 189 patients needed a device provided by the investigators. Patient’s adherence to the daily digital symptom diary was excellent during the entire study period, reflected by a mean (SD) completion rate of 87.9% (9.4), 91.5% (9.2) and 86.9% (10.8), during all 70 days of study duration, the 14-day pre-treatment period, and the eight-week treatment period, respectively. Adherence during the treatment period did not differ significantly between treatment groups being 87.2% for placebo, 88.3% for the small-intestinal release ( P =0.67 versus placebo), and 87.2% for the ileocolonic release peppermint oil ( P =0.33 versus placebo). Adherence did not differ between patients that were clinical responders to treatment versus patients that were non-responders, i.e. 88.0% and 86.2%, respectively. Over the complete study period of 70 days, a significant decrease in mean weekly patient’ adherence to the end-of-day questionnaire was found, i.e. F (5.9, 1114.9)=15.5, P <0.001 ( Figure 9.4 ). Nevertheless, mean (SD) adherence was still good at the end of the study, i.e. 79.6% (26.61) ( Figure 9.4 ).