High risk of overdose death following release from prison: variations in mortality during a 15-year observation period.

BACKGROUND AND AIMS: The time post-release from prison involves elevated mortality, especially overdose deaths. Variations in overdose mortality both by time since release from prison and time of release has not been investigated sufficiently. Our aims were to estimate and compare overdose death rates at time intervals after prison release and to estimate the effect on overdose death rates over calendar time.

DESIGN, SETTING, PARTICIPANTS, MEASUREMENTS: This 15-year cohort study includes all individuals (n = 91 090) released from prison (1 January 2000 to 31 December 2014) obtained from the Norwegian prison registry, linked to the Norwegian Cause of Death Registry (2000-14). All-cause and cause-specific mortality were examined during different time-periods following release: first week, second week, 3-4 weeks and 2-6 months, and by three different time intervals of release. We calculated crude mortality rates (CMRs) per 1000 person-years and estimated incidence rate ratios (IRR) by Poisson regression analysis adjusting for time intervals after prison release, release periods and time spent in prison.

FINDINGS: Overdose deaths accounted for 85% (n = 123) of all deaths during the first week following release (n = 145), with a peak during the 2 days immediately following release. Compared with week 1, the risk of overdose death was more than halved during week 2 [IRR = 0.43; 95% confidence interval (CI) = 0.31-0.59] and reduced to one-fifth in weeks 3-4 (IRR = 0.22; 95% CI = 0.16-0.31). The risk of overdose mortality during the first 6 months post-release was almost twofold higher in 2000-04 compared with 2005-09 (IRR = 0.53; 95% CI = 0.43-0.65) and 2010-14 (IRR = 0.47; 95% CI = 0.37-0.59). The risk of overdose death was highest for those incarcerated for 3-12 months compared with those who were incarcerated for shorter or longer periods, and recidivism was associated with risk of overdose death.

CONCLUSIONS: There is an elevated risk of death from drug overdose among individuals released from Norwegian prisons, peaking in the first week. The risk has reduced since 2000-04, but is greatest for those serving 3-12 months compared with shorter or longer periods.