The Effect of Serious Mental Illness on the Risk of Rehospitalization Among Patients With Diabetes

Background Medical-surgical rehospitalizations within a month after discharge among patients with diabetes result in tremendous costs to the US health care system. Objective The study's aim was to examine whether co-morbid serious mental illness diagnoses (bipolar disorder, schizophrenia, or other psychotic disorders) among patients with diabetes are independently associated with medical-surgical rehospitalization within a month of discharge after an initial hospitalization. Methods This cohort study of all community hospitals in Washington state evaluated data from 82,060 adults discharged in the state of Washington with any International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis indicating diabetes mellitus between 2010 and 2011. Data on medical-surgical hospitalizations were obtained from the Washington State Comprehensive Hospital Abstract Reporting System. Co-morbid serious mental illness diagnoses were identified based on International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes indicating bipolar disorder, schizophrenia, or other psychotic disorders. Logistic regression analyses identified factors independently associated with rehospitalization within a month of discharge. Cox proportional hazard analyses estimated time to rehospitalization for the entire study period. Results After adjusting for demographics, medical co-morbidity, and characteristics of the index hospitalization, co-morbid serious mental illness diagnosis was independently associated with increased odds of rehospitalization within 1 month among patients with diabetes who had a medical-surgical hospitalization (odds ratio: 1.24, 95% confidence interval: 1.07, 1.44). This increased risk of rehospitalization persisted throughout the study period (up to 24mo). Conclusions Co-morbid serious mental illness in patients with diabetes is independently associated with greater risk of early medical-surgical rehospitalization. Future research is needed to define and specify targets for interventions at points of care transition for this vulnerable patient population.