Postoperative opioid use in Norway-a population-based observational study on patterns of long-term use.

Background: The utilization patterns of opioid analgesics and the proportion of long-term opioid use after surgery in Norway is largely unknown.

Methods: This study aimed to estimate the proportion of one-year long-term prescription opioid use among all Norwegian postoperative opioid users. Complete data from central health registries (NPR, NorPD, Statistics Norway, CoDR) were linked via the personal identification number unique to all citizens. The study period was January 1st 2010 until December 31st 2019. Long-term opioid use was defined as at least two opioid dispensings within two subsequent 90-day periods, with a minimum average use of 10 MME/day for the first 90 days.

Results: The study population consisted of 693 495 post-operative opioid users (53.6% women), whereof 73.2% had not used opioids the year before surgery (new users). Among the postoperative opioid users, 3.8% were one-year long-term opioid users. The corresponding figures for new and previous opioid users were 0.4% and 13.1%, respectively. The highest proportions of long-term opioid use were found after transluminal endoscopy, eye surgery and assessments related to surgical procedures. In previous opioid users, the proportion of one-year long-term use was higher among women than men in all age groups, a difference that increased with age.

Conclusions: The proportion of postoperative long-term opioid use in Norway is generally low. We detected higher proportions of long-term opioid use after certain types of surgery, but our crude surgery definition warrants further examination. Previous opioid users pose a particular challenge in the management of postoperative pain.

Trial registration: The study used national health registry data from the period 2010-2019. A pre-registered analysis plan is available at Open Science Framework.