Excess mortality following discharge from substance use disorder treatment in Chile

BACKGROUND AND AIMS: People with substance-use disorders (SUDs) have increased mortality risk, yet Chilean estimates of SUD-based mortality are scarce. This study aimed to quantify all-cause and cause-specific mortality following SUD treatment in Chile compared with the general population and assess variation across key clinical and demographic subgroups. DESIGN: National-level registry-based retrospective data linkage cohort study. SETTING: Publicly funded SUD psychosocial treatments offered by the Chilean National Drug Agency, linked with official national mortality records from 2010 to 2020. PARTICIPANTS: 70064 adults aged 18-64 years (24% women, median age 35 at treatment entry) were followed after their first treatment episode until death or 31 December 2020. MEASUREMENTS: Primary outcome was all-cause mortality. Secondary outcomes were cause-specific mortality by the International Classification of Diseases, 10th revision, underlying and external causes. We estimated age-sex-calendar year directly standardized rates (DSR), and standardized mortality ratios (SMR) compared with the expected rate for the (sub)population. We also stratified rates and ratios by sex (men/women), attained age (18-29, 30-44, 45-59, 60+), setting (ambulatory/residential), primary substance (alcohol; illicit: predominantly cocaine paste base, marijuana and cocaine hydrochloride) and treatment compliance (not completed/completed). Additionally, we estimated rates and SMRs for underlying and external causes of mortality. FINDINGS: Over a median 4.9-year follow-up (353 826 person-years), 2996 deaths occurred [DSR = 10.6, 95% confidence interval (CI) = 8.6-13.1]. Overall SMR was 3.65 (95% CI = 3.52-3.79). Excess risk was particularly pronounced for women (SMR = 5.57, 95% CI = 5.14-6.03), patients admitted due to alcohol use disorder (SMR = 4.59, 95% CI = 4.33-4.86), in residential care (SMR = 4.91, 95% CI = 4.45-5.42) and treatment noncompletion (SMR = 4.04, 95% CI = 3.85-4.24). Cause-specific mortality revealed elevated external-cause excess risk for SUD patients, including intentional self-harm (SMR = 6.67, 95% CI = 6.05-7.36), unintentional injuries (SMR = 5.37, 95% CI = 4.79-6.02) and assaults (SMR = 4.98, 95% CI = 4.16-5.96). Notable excess risk was also observed for non-external mortality causes: digestive system (SMR = 8.20, 95% CI = 7.62-8.83), symptoms and signs (SMR = 5.18, 95% CI = 4.29-6.26) and respiratory diseases (SMR = 5.18, 95% CI = 4.47-5.99) were greater than expected. CONCLUSIONS: In Chile, patients with a history of publicly funded substance-use disorder treatment appear to have an all-cause mortality up to 3.7 times higher than the general population, driven predominantly by digestive and respiratory causes, as well as self-harm, unintentional injuries and assaults.