Fatal Overdoses in a Cohort of Chronic Pain Patients

Background: Chronic pain patients may be at an increased risk of drug overdoses due to heightened access to prescription drugs such as opioids and frequent comorbid psychiatric disorders. However, there is little research as to what characterizes chronic pain patients who die of overdoses.

Objectives: To describe persons who died of an overdose and to compare their medical diagnoses and demographic characteristics to age- and gender-matched controls in a cohort of chronic pain patients.

Methods: We utilized a nested case-control design, extracting data from nationwide health registers in Norway. All persons with filled prescriptions reimbursed for chronic pain were identified in 2010-2019, forming the baseline cohort. People with drug overdose as a cause of death in 2010-2019 were matched with a maximum of 10 controls by gender and age at cohort entry. Data on primary and secondary healthcare diagnoses were extracted in 2008-2019 and demographic and drug dispensation data in 2010-2019.

Results: Overall, 623 persons died of an overdose in 2010-2019. They were on average 48.5 years old and 57.3% were men. Most, 66.8%, had overdosed non-intentionally and 61.8% due to pharmaceutical opioids, excluding methadone. In the last three months, 65.7% had been dispensed opioids, 70.6% benzodiazepines or benzodiazepine-related hypnotics, and 52.3% both. Compared to the 62,245 controls, individuals who had died from an overdose had more frequently diagnosed depression (68.1% [95% confidence interval, 64.2 - 71.7] vs. 33.1% [32.8 - 33.5]), anxiety (60.2% [56.2 - 64.0] vs. 22.6% [22.3 - 22.9]), substance use disorders (70.5% [66.7 - 74.0] vs. 13.9% [13.7 - 14.2]), previous suicide attempts (21.2% [18.1 - 24.6] vs. 2.4% [2.3 - 2.6]), and non-fatal poisonings with pharmaceuticals (35.5% [31.7 - 39.4] vs. 2.7% [2.6-2.9]). The individuals who had died of an overdose were less frequently born outside Norway (5.9% [4.3 - 8.2] vs. 18.8% [18.5 - 19.1]) and had less frequently attained a university-level education (11.7% [9.4 - 14.6] vs. 20.7% [20.4 — 21.0]) compared to matched controls.

Conclusions: Among persons with chronic pain, overdose deaths were connected to substantial psychiatric morbidity and frequent prescription drug use prior to death. High proportions of non-intentional overdoses and of pharmaceutical opioids as the cause can be considered alarming for prescribers and other healthcare professionals.