Mortality among individuals accessing pharmacological treatment for opioid dependence in California, 2006-10

Abstract

Aims: To estimate mortality rates among treated opioid-dependent individuals by cause and in relation to the general population, and to estimate the instantaneous effects of opioid detoxification and maintenance treatment (MMT) on the hazard of all-cause and cause-specific mortality.

Design: Population-based treatment cohort study.

Setting: Linked mortality data on all individuals first enrolled in publicly funded pharmacological treatment for opioid dependence in California, USA from 2006 to 2010.

Participants: A total of 32 322 individuals, among whom there were 1031 deaths (3.2%) over a median follow-up of 2.6 years (interquartile range = 1.4-3.7).

Measurements: The primary outcome was mortality, indicated by time to death, crude mortality rates (CMR) and standardized mortality ratios (SMR).

Findings: Individuals being treated for opioid dependence had a more than fourfold increase of mortality risk compared with the general population [SMR = 4.5, 95% confidence interval (CI) = 4.2, 4.8]. Mortality risk was higher (1) when individuals were out-of-treatment (SMR = 6.1, 95% CI = 5.7, 6.5) than in-treatment (SMR = 1.8, 95% CI = 1.6, 2.1) and (2) during detoxification (SMR = 2.4, 95% CI = 1.5, 3.8) than during MMT (SMR = 1.8, 95% CI = 1.5, 2.1), especially in the 2 weeks post-treatment entry (SMR = 5.5, 95% CI = 2.7, 9.8 versus SMR = 2.5, 95% CI = 1.7, 4.9). Detoxification and MMT both independently reduced the instantaneous hazard of all-cause and drug-related mortality. MMT preceded by detoxification was associated with lower all-cause and other cause-specific mortality than MMT alone.

Conclusions: In people with opiate dependence, detoxification and methadone maintenance treatment both independently reduce the instantaneous hazard of all-cause and drug-related mortality.

Keywords: Administrative data; detoxification and maintenance treatment; longitudinal design; mortality; opioid dependence.

Figure 1. Crude mortality rates by cause of death according to in-treatment and out-of-treatment periods

^ˆ overdose (accidental poisoning by alcohol or other drugs), other drug-related (harmful alcohol or drug use or dependence) + suicide (intentional self-harm or self-poisoning), homicide, injury (accidental injury, traffic accidents) # cancer, respiratory disease, liver disease, diabetes, infections/parasites, endometriosis, digestive disease, renal disease, central nervous system, other, and unknown See Appendix 1 for ICD-10 codes incldued in each category of mortality.