Applying accelerated failure time frailty model using Bayesian approach to identify some risk factors of time to relapses in schizophrenia patients

 Introduction: Schizophrenia is a severe mental disorder and one of its important features is repetition of relapses over time. The aim of this study was to identify some risk factors of relapse time in schizophrenia patients using Weibull parametric accelerated failure time frailty model in survival analysis with Bayesian approach. Materials and Methods: In this retrospective longitudinal study, the data was extracted from records of 159 schizophrenia patients with at least one relapsein Razi Psychiatric ٍEducational-Medical Centre in Tehran. In survival analysis, the times of relapses of schizophrenia are known as recurrent events times. To identify some risk factors of these times, Weibull accelerated failure time frailty model was fitted to the data and analyzed by Bayesian approach using WinBUGS software to estimate accelerated factors and their credible intervals for significance testing. Results: 28.7% of males and 12% of females had experienced 9 to 14 times of relapse. Among the studied factors, age at onset (CI95%: (-0.09, -0.07), gender (CI95%: (-0.87, -0.21)), marital status CI95%: (-1.12, -0.55) and family history of schizophrenia (CI95%: (-0.67, -0.17) were identified as significant risk factors for the times of occurred relapses, but the mode of onset and a history of head injury was not a significant risk facor. There was a significant correlation (frailty parameter) among the relapses times (CI95%: (0.24, 0.58)), too. Conclusion: Existing correlation among relapse times requires continued efforts. To decrease relapse probability especially in patients who experience relapses in low ages, single, male and patients with family history of schizophrenia, special preventive and treatment efforts is recommended. Not uniform registration of other variables in the records, made identifying other risk factors not possible