Background: Thirty to forty-five percent of ulcerative colitis (UC) patients show non-adherence to aminosalicylates, and non-adherence has been reported to increase the risk of clinical relapse. Because Japan differs from Western countries in terms of health care and drugs administered, adherence to aminosalicylates in Japan may differ from that elsewhere. Therefore, we examined aminosalicylate adherence and its relationship to the risk of clinical relapse of UC in Japan. Methods: A 1-year, prospective cohort study was conducted in 104 outpatients with UC in remission who had taken aminosalicylates >6 months. Aminosalicylate adherence was evaluated using data from a self-administered questionnaire and medical records. Non-adherence was defined as taking <80 % of the prescribed dose of aminosalicylates. The primary outcome was the record of clinical relapse in medical charts. Results: Twenty-nine patients (27.9 %) were evaluated as showing non-adherence. Among all subjects, 24 patients (23.1 %) relapsed. The non-adherence group had a higher rate of 1-year relapse than did the adherence group (41.3 vs. 16.0 %). Multiple Cox regression analysis showed that non-adherence increased the risk of clinical relapse 2.3-fold (hazard ratio 2.3, 95 % confidence interval 1.004-5.24, p = 0.04). Conclusions: Although the adherence rate in this study was slightly higher than that in previous studies, Japanese patients with UC who were not adherent to their medications had a twofold greater risk of relapse than those who were. These results indicate the importance of early identification of patients with non-adherence. A program to support medication taking behavior is needed to prevent UC relapse.
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