Opioid use was associated with more difficulty falling asleep among adults with chronic pain, according to a recent study. However, this cross-sectional effect was only significant among those reporting lower pain intensity. Researchers speculate that this effect is masked among those with severe pain because the pain-related sleep debt they acquire throughout the night then facilitates sleep onset the next day. Participants (n=144; 95% female; mean age=51.6, SD=11.4) completed assessments of insomnia symptoms, pain, and use of sleep/pain medication. Multiple regression was used to determine if pain intensity moderates the association between opioid use (yes/no) and sleep onset latency (SOL), wake after sleep onset (WASO), sleep quality, or time in bed. They found:

• Stronger pain intensity was associated with longer self-reported WASO and worse sleep quality, independent of opioid use.
• Conversely, opioid use was associated with longer time in bed, independent of pain intensity.
• Opioid use and pain intensity interacted in the prediction of SOL, such that opioid use (vs non-use) was associated with longer SOL in the context of mild but not moderate to severe pain intensity.