Fatal overdoses and deaths by other causes in a cohort of Norwegian drug abusers—A competing risk approach

ObjectiveTo identify causes of death among Norwegian drug abusers and to investigate the risk factors for fatal overdose and other causes of death, with specific attention to ageing and duration of abuse.MethodsIn a cohort of 501 drug abusers admitted to treatment in the period 1981–1991, mortality has been calculated as incidence rates. The analyses of time to death were conducted as proportional hazard regression models using a competing risk approach.ResultsCrude incidence rates for all deaths and overdose deaths did not vary with age. For non-overdose deaths, however, the incidence was significantly higher after the age of 40. Explanatory factors associated with age at fatal overdoses are also associated with age at death by other causes. At every age the risk of death was higher with a long-term abuse of drugs, and more so for fatal overdose than for death by other causes.ConclusionsWith respect to fatal overdose duration of abuse, but not ageing, is found to be a risk factor. With respect to death by other causes both ageing and duration of abuse are factors associated with such death.