Background: The exacerbation of disease in patients with ulcerative colitis (UC) can greatly affect quality of life and can impose economic burdens. In Japan, a large nationwide registry for the medical reimbursement of UC patients has existed since 1975. We aimed to examine factors associated with UC exacerbation among patients newly diagnosed with mild UC using electronic data from the registry. Methods: We retrospectively reviewed the clinical data of patients (n = 8120) newly diagnosed with mild UC between 2003 and 2011, and examined the association of patient background, medications, clinical symptoms and laboratory data, and pathological findings with exacerbation of UC, using the Cox proportional hazards model. Results: The incidence of UC exacerbation was 94.6 per 1000 person-years (mean follow-up of 2.1 years). We found that male sex, age <17 years, an extensive lesion (left-sided colitis or pancolitis), overweight or obesity, hematochezia (mild or moderate-to-severe), mushy stools, frequency of bowel movements, and crypt architectural distortion were positively associated with UC exacerbation. On the other hand, age >40 years, high hemoglobin concentration, and high serum albumin levels were inversely associated with UC exacerbation among patients with mild UC in Japan. Conclusion: Using data from the Japanese nationwide registry, we identified several factors, including body mass index and pathological findings, associated with disease exacerbation among patients with newly diagnosed mild UC. Our findings may lead to earlier recognition of exacerbation in patients with mild UC, thus enabling optimal care.
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