Mental illness related disparities in potentially preventable hospitalisations: A population-based cohort study

Background Emerging evidence indicates an association between mental illness and poor quality of physical health care. We compared the quality of primary care provided to mental health clients (MHCs) with non-MHCs, using potentially preventable hospitalisations (PPHs) as an indicator. Methods Population-based cohort study of 139,208 MHCs and 294,180 matched non-MHCs in Western Australia from 1990 to 2006, using linked data from electoral roll registrations, mental health registry (MHR) records, hospital admissions and deaths. We used the electoral roll as the sampling frame for both cohorts to enhance internal validity of the study, and the MHR to separate MHCs from non-MHCs. Rates of PPHs (overall and by PPH category and condition) were compared between MHCs, category of mental disorders and non-MHCs. Multivariate negative binomial regression analyses adjusted for sociodemographics and case mix. Results Diabetes and its complications, adverse drug events (ADEs), chronic obstructive pulmonary disease (COPD), convulsions and epilepsy, and heart failure were the most common causes of PPHs in MHCs. Compared with non-MHCs, MHCs with any mental disorders were more likely to experience a PPH than non-MHCs (adjusted rate ratio (ARR) 2.059, 95% CI 2.026-2.093). ARRs of PPHs were highest for convulsions and epilepsy, nutritional deficiencies, COPD and ADEs. The risk of a PPH was highest in MHCs with alcohol/drug disorders, affective psychoses, other psychoses and schizophrenia. Conclusions MHCs have a significantly higher risk of PPHs than non-MHCs. Improved primary and secondary prevention is warranted, especially at the primary care level.