Mortality among clients seeking treatment for buprenorphine abuse in Finland

BACKGROUND: It is unclear whether buprenorphine abuse is associated with a similar risk of death to other substance abuse. This study examined all-cause mortality rates and causes of deaths among clients seeking treatment for buprenorphine abuse.

METHODS: Structured clinical interviews were conducted with 4685 clients between January 1998 and August 2008. Records of deaths that occurred among these clients were extracted from the Official Causes of Death Register in Finland. Standardized mortality ratios (SMRs) with 95% confidence intervals (CI) were computed using national mortality rates over a 13-year follow-up to examine excess mortality. Kaplan-Meier survival analysis was used to compare survival between buprenorphine and other clients.

RESULTS: Sixty-one of 780 (7.8%) clients who sought treatment for buprenorphine abuse and 408 of 3905 (10.4%) other clients died during the 13-year follow-up period. The most common cause of death was drug-related in buprenorphine (n=25, 41.0%) and other clients (n=142, 34.8%). Survival rates were similar among buprenorphine and other clients (log-rank χ[df=1](2)=0.215, p=0.643). The SMR was 3.0 (95% CI 2.3-3.8) and 3.1 (95% CI 2.8-3.4) for buprenorphine and other clients, respectively. Excess mortality was highest among women aged 20-29 years, and more pronounced in buprenorphine clients (SMR 27.9 [95% CI 12.6-49.0]) compared to other clients (SMR 14.0 [95% CI 9.3-19.6]).

CONCLUSIONS: Clients seeking treatment for buprenorphine abuse had a three times higher mortality rate than the national average, with the excess risk highest among female clients. Overall mortality rates were similar among clients seeking treatment for buprenorphine and other substance abuse.