Predictors of Medical Hospitalization in Older Adults with Severe Mental Illness

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Introduction: Medical comorbidity is very prevalent in older adults with mental illness. Medical comorbidity has been shown to be influenced by age, psychiatric diagnosis, the total number of non-psychotropic drugs and other factors. However, medical health service utilization has not yet been studied in this vulnerable population. Our objectives were to 1) quantify the rate of medical re-hospitalization in a geriatric psychiatry population and 2) to identify clinical and demographic characteristics that can predict medical re-hospitalisation. Methods: This is a retrospective study of geriatric psychiatric inpatients admitted to a tertiary care Canadian inpatient psychiatric unit between 2003 and 2008. We ascertained the incidence of medical admission in the 5 year period following discharge from the index psychiatric hospitalization (e.g. 2008-2013 if a patient had been first admitted in 2008). Using Pearson Chi-Square and Student t-tests, we examined the correlation between medical hospitalization and various clinical and demographic variables. Subsequently, using multivariate time-to-event analyses, we examined whether certain clinical and demographic variables were independently associated with medical hospitalization (e.g. Age, Bipolar Disorder and Psychotic Disorder). Results: 226 geriatric patients (> age 65) were admitted between 2003 and 2008. Over 5-year follow-up, 120 (53.1%) patients were hospitalized at least once for a medical condition. On bivariate analysis, increased age (p1⁄40.006), the presence of a previous psychiatric hospitalization, bipolar disorder, and the absence of a psychotic disorder (schizophrenia/schizoaffective disorder) were associated with trends increased probability of medical hospitalization (p<0.10). However in cox-regression analysis, only increased age independently predicted a lower time to medical hospitalization (HR1⁄4 1.04/year of increasing age, (95%CI 1.02-1.07), p1⁄40.01). Conclusions: Our data suggests that medical hospitalization is very common in older adults with severe mental illness: 53.1% over 5-year follow-up. Furthermore, despite previous data suggesting that geriatric psychiatry patients are a “survivor cohort” with regards to medical comorbidity, increasing age was the strongest predictor of medical hospitalization. Every year of life was associated with a 4% elevation in risk, which translates into a 55% increase in risk between age 65 and 85. Clinicians taking care of geriatric patients admitted to inpatient psychiatry should be vigilant about the high risk of medical hospitalization particularly in those with advanced age. Future interventions could be tailored towards this population to prevent medical health service utilization and promote good physical health.