Causes of death among patients in opioid maintenance treatment in Norway

Background: Opioid dependence is associated with high rates of morbidity and mortality. It is well established that opioid maintenance treatment (OMT) reduces mortality among opioid dependent persons, but mortality is still high compared to the general population. In Norway, OMT is delivered within the national OMT programme. The treatment is characterised by an ageing OMT-population, with high retention, and buprenorphine as first-line treatment. Earlier Norwegian studies found non-overdose deaths to be the most common cause of death during OMT. However, available data for Norway are almost 20 years old, and there is no recent record linkage with mortality registers. To improve treatment and prevent premature mortality, more research is warranted to better understand the complexity of different mortality rates and causes of death during OMT. Preliminary results were presented at the Lisbon Addictions conference in 2017, and now we present updated data on mortality and causes of death during OMT in Norway.

Aim: The aim of the study is to explore and describe mortality among patients in opioid maintenance treatment in Norway in the years 2014 and 2015.

Methods and material: The study was observational, with a descriptive and explorative cross-sectional design. The sample­ comprised all patients who died during treatment or less than five days after the last intake of OMT-medication, between 1 January 2014 and 31 December 2015. Data from the Norwegian Cause of Death Registry and the Norwegian Patient Registry were merged with data from medical records in the public specialist health care service.

Results: 200 patients died during OMT. Forensic or clinical autopsy was performed in 63% of the cases. The mean age at time of death was 48.9 years (SD 8.4), range 23-71 years, and 73% were male. The crude mortality rate during OMT was 1.4 per 100 person-years (PY). The most common cause of death was somatic disease (45%), followed by drug-related deaths (42%). Suicide, accident or homicide was the cause of death for 12% of the patients. High somatic mortality among older OMT-patients have also been found in earlier studies, but in our study, cancer and lung diseases alone caused 23% of all deaths during OMT.

Conclusions: Both somatic disease and drug-related deaths were common causes of death in the ageing OMT-population in Norway. Clinicians need to be aware that OMT-patients face somatic problems far earlier than the general population. The high prevalence of cancer and lung diseases may indicate that patients who smoke should be offered spirometry and cancer screening. Focus on tobacco harm-reduction approaches and smoking cessation is highly needed. Continuous work with overdose prevention is also essential.