What Explains Poor Health-related Quality of Life Associated With Opioid Use Among Adults With Chronic Noncancer Pain Conditions? A Blinder-Oaxaca Decomposition

Objectives: The objective of this study was to estimate the extent to which differences in person-level characteristics between opioid users and nonusers contribute to poor healthrelated quality of life (HRQoL) of long-term opioid users with chronic noncancer pain condition (CNCP). Materials and Methods: We conducted a retrospective cohort study of adults (n=5917) using longitudinal data from multiple years of Medical Expenditure Panel Survey. Adults with CNCPwere classified into short-term, long-term, and opioid nonusers. We measured HRQoL with physical component summary (PCS) and mental component summary (MCS) scores from the Short-Form 12 Questionnaire. A regression decomposition analysis of results from linear regression was performed. Results: Among adults with CNCP, 17.8% and 17.2% reported long-term and short-term opioid use, respectively. Longterm opioid users had lower PCS scores (β=−4.48; P<0.001) as compared with nonusers, even after adjusting for other independent variables. There were no statistically significant associations of long-term opioid use to MCS and short-term opioid use to both PCS and MCS scores. Postlinear regression decomposition analyses revealed that 44.8% of the difference in PCS scores (−3.76 of −8.41) was explained by differences in employment, physical activity, number of CNCP, and other chronic conditions, and use of nonopioid pain medications between long-term opioid users and nonusers. Conclusions: Long-term opioid use was associated with lower HRQoL. The difference in HRQoL between long-term opioid users and nonusers was explained by both modifiable and nonmodifiable patient characteristics. Our findings suggest that improving HRQoL among long-term opioid users may require interventions and policies both within and beyond health care.