Trajectories of opioid use among patients with low back pain: Association to work absence.

Background: Low back pain (LBP) is a leading reason for opioid use and a closer examination of opioid use and productivity losses among these patients is needed. We identify opioid use trajectories using a group-based trajectory model (GBTM) and estimate productivity losses across the trajectories.

Methods: Patients diagnosed with LBP in Swedish specialty care between 2011 and 2015, between the ages of 20 and 60, were included. Two GBTMs were estimated on monthly opioid use (converted to oral morphine equivalents) during the two 12-month periods preceding and following diagnosis. Productivity losses were estimated using the human-capital approach.

Results: In total, 147,035 patients were included. The mean age at diagnosis was 43 years of age and 49% of the patients were male. A qualitative assessment of the identified groups in the GBTM models was made based on the patterns of opioid use. We chose three pre-diagnosis groups characterized as 'Pre-low' (N = 109,492), 'Pre-increase' (N = 27,336) and 'Pre-high' (N = 10,207). Similarly, four post-diagnosis groups were chosen and characterized as 'Post-low' (N = 73,287), 'Post-decrease' (N = 39,446), 'Post-moderate' (N = 20,001) and 'Post-high' (N = 13,595). Only 50% of the patients in the 'Pre-high' group were in the 'Post-high' group. The total productivity losses by the pre-diagnosis groups were more than 2.7 billion Euros over the total 6-year study period.

Conclusion: This study highlights how patients with LBP and high use of opioids are highly correlated before and after diagnosis. Patients with high use of opioids also exhibit high work absence and productivity losses.

Significance statement: This was the first study to estimate trajectories of opioids in the two time periods before and after a diagnosis of low back pain. For the first time, productivity losses were also estimated across the identified opioid use trajectories.