Investigating cognitive function among people with chronic non-cancer pain prescribed opioids: a longitudinal study

Background: Opioid medications are commonly prescribed for chronic non-cancer pain (CNCP), but may impair important cognitive functions (e.g., memory). The present paper reports preliminary results from an ongoing longitudinal study objectively assessing cognitive function in individuals prescribed opioids for CNCP, compared to opioid-free controls.

Methods: In this mixed 2(group: using prescribed opioids, opioid-free) x2(time: baseline, 3 months) observational longitudinal design, participants (18-65 years) report medication use and pain, and completed a cognitive battery. Stress tolerance and choice reaction time are measured on the Determination Test (DT) and Reaction Time Test (RT), respectively. Scores are reported as percentile ranks (PRs) based on a healthy population.

Results: Chronic back/neck pain was the most frequently reported condition (46.7%) among the opioid group (n = 15; 11 female); tramadol was the most commonly used opioid (40.0%). Preliminary results at baseline showed that one-third (33.4%) of the opioid group scored below the 50th percentile on the DT; 6.7% scored below the 25th percentile. For RT, one-third (33.3%) of participants scored below the 25th percentile. Results were relatively consistent at 3 months (DT: 35.7% <50th percentile; RT: 21.4% <25th percentile). Given this, significant time*group interaction effects are not anticipated.

Conclusions: On two measures, one-third of the sample scored lower than 50% (DT) and 75% (RT) of the general population; however, cognitive deficits did not appear to worsen over time with continued use. Data from both groups and the wider battery (examining domains such as processing speed, inhibitory control, and memory) may more sensitively identify any other cognitive effects of chronic medication use. Given the initial findings of stable cognitive effects, clinical interventions should focus primarily on consumer education and monitoring of cognition in the early stages of opioid therapy.