Risk of discharge against medical advice among hospital inpatients with a history of opioid agonist therapy in New South Wales, Australia: A cohort study and nested crossover-cohort analysis

Background: People who use illicit opioids have high rates of hospital admission. We aimed to measure the risk of discharge against medical advice among inpatients with a history of opioid agonist therapy (OAT), and test whether OAT is associated with lower risk of discharge against medical advice. Methods: We conducted a cohort study of patients admitted to hospital in an emergency between 1 August 2001 and 30 April 2018 in New South Wales, Australia. All patients had a previous episode of OAT in the community. The main outcome was discharge against medical advice, and the main exposure was whether patients had an active OAT permit at the time of admission. Results: 14,035/116,957 admissions (12 %) ended in discharge against medical advice. Admissions during periods of OAT had 0.79 (0.76-0.83; p < 0.001) times the risk of discharge against medical advice, corresponding to an absolute risk reduction of 3.0 percentage points. Risk of discharge against medical advice was higher among patients who were younger, male, identified as Aboriginal and/or Torres Strait Islander, and those admitted for accidents, drug-related reasons, or injecting-related injuries (such as cutaneous abscesses). In a subsample of 7793 patients included in a crossover-cohort analysis, OAT was associated with 0.84 (95 % CI 0.76 0.93; p < 0.001) times the risk of discharge against medical advice. Conclusions: Among patients with a history of OAT, one in eight emergency hospital admissions ends in discharge against medical advice. OAT enrolment at the time of admission is associated with a reduction of this risk.