Perforated appendicitis in patients with schizophrenia: a retrospective cohort study

OBJECTIVE Altered pain sensitivity may affect the outcome of appendicitis in patients with schizophrenia. We aimed to compare the prevalence of perforation in appendicitis between patients with and without schizophrenia. DESIGN Retrospective cohort study with random matching. SETTING A single tertiary medical centre in Japan. PARTICIPANTS From 1985 to 2013, 1821 cases of appendicitis requiring appendectomy were collected. Patients with schizophrenia and a cohort of randomly selected control subjects without schizophrenia who underwent appendectomy were identified. PRIMARY AND SECONDARY OUTCOME MEASURES The primary outcome was the rate of perforated appendicitis in patients with and without schizophrenia. Secondary outcome was the odds of perforated appendicitis by different clinical factors. RESULTS 62 patients with schizophrenia and randomly sampled 200 non-schizophrenic patients were compared. The prevalence of perforation was 53% in patients with schizophrenia versus 17% in controls (p<0.0001). The adjusted OR for perforation were 4.87 (95% CI: 2.33 to 10.2) for schizophrenia, 3.35 (95% CI 1.51 to 7.45) for age >55 years and 2.18 (95% CI: 1.12 to 4.27) for delayed presentation. CONCLUSION Appendiceal perforation was more frequent in patients with schizophrenia than controls, which may be partly attributable to delayed presentation and altered responses to pain.