Application of mixture distributions for identifying thresholds of frequent and high inpatient mental health service use in longitudinal data.

BACKGROUND: There is a need for greater understanding about frequent and high use of inpatient mental health services, and those with ongoing increased needs. Most studies employ a threshold of frequent use (e.g. numbers of admissions) and high use (e.g. lengthy stays) without justification. AIMS: To identify model-driven thresholds for frequent/high inpatient mental health service use and contrast characteristics of patients identified using various models and thresholds. METHOD: Retrospective population-based study using 12 years of longitudinal data for 5631 patients admitted with a mental health diagnosis. Two-component negative binomial and poisson mixture (truncated/untruncated) models identified thresholds for frequent/high use in a 12-month period. RESULTS: The two-component negative binomial mixture model resulted in the best model fit. Using negative binomial-derived thresholds, 5.3% of patients had a period of frequent use (admitted six or more times), 15.8% of high use (hospitalised for 45 or more days) and 3.5% of heavy use (both frequent and high use). The prevalence of specific mental health disorders (e.g. mood disorder and schizophrenia) among frequent and high use cohorts varied across thresholds. CONCLUSIONS: This model-driven approach can be applied to identify thresholds in other cohorts. Threshold choice may depend on the magnitude and focus of potential interventions.

Predisposing, enabling and need factors associated with increased use and ongoing increased use of inpatient mental health care: A population-based longitudinal study.

OBJECTIVE: The study investigated factors associated with frequent (admissions), high (total length of stay) or heavy (frequent and high) hospital use, and with ongoing increased hospital use, for mental health conditions in a regional health district. METHODS: A retrospective population-based study using longitudinal hospital, emergency department and community service use data for people admitted with a mental health condition between 1 January 2012 and 31 December 2016. Multivariate logistic regression models assessed the association of predisposing, enabling and need factors with increased, and ongoing increased, hospital use. RESULTS: A total of 5,631 people had at least one mental health admission. Frequent admission was associated with not being married (odds ratio = 2.3, 95% confidence interval = [1.5, 3.3]), no private hospital insurance (odds ratio = 2.2, 95% confidence interval = [1.2, 3.8]), previous mental health service use (community, emergency department, lengthy admissions) and a history of a substance use disorder, childhood trauma, self-harm or chronic obstructive pulmonary disease. High and heavy hospital use was associated with marital status, hospital insurance, admission for schizophrenia, previous mental health service use and a history of self-harm. Ongoing frequent use was less likely among those aged 65 and older (odds ratio = 0.2, 95% confidence interval = [0.1, 1.0]) but more likely among those with a history of depression (odds ratio = 2.2, 95% confidence interval = [1.1, 4.4]). Ongoing high use was also associated with admissions for schizophrenia and a history of self-harm. CONCLUSION: Interventions targeted at younger people hospitalised with schizophrenia, a history of depression or self-harm, particularly with evidence of social and or health disadvantage, should be considered to improve long-term consumer and health system outcomes. These data can support policymakers to better understand the context and need for improvements in stepped or staged care for people frequently using inpatient mental health care.