MILWAUKEE – Individuals with chronic pain frequently have disrupted sleep and also may be at risk for opioid use disorder. However, even with advanced monitoring, it’s not clear how sleep modulates pain and opioid cravings.
Sleep has an impact on positive and negative affect, but new research shows that the link between sleep and mood states that may contribute to opioid use disorder is not straightforward. At the scientific meeting of the American Pain Society, Patrick Finan, PhD, of Johns Hopkins University, Baltimore, discussed how sleep and mood affect cravings for opioids among those in treatment for opioid use disorder (OUD).
said Dr. Finan, who told attendees that one key question he and his colleagues were seeking to answer was whether those with OUD and chronic pain had more disturbed sleep than those with OUD alone. Also, the researchers wanted to know whether the ups and downs of sleep on a day-to-day basis were reflected in pain scores among those with OUD, as would be predicted by prevailing models.
Finally, two “proximal indicators” of relapse risk, affect and heroin craving, might be affected by both sleep and pain, and Dr. Finan and collaborators sought to explore that association.
The work was part of a larger study looking at the natural history of OUD and OUD with comorbid chronic pain. To participate in this parent study, adults with OUD had to be seeking treatment or currently enrolled in methadone or buprenorphine maintenance treatment, and without current major depressive disorder. Also, patients could not have a history of significant mental illness, cognitive impairment, or a medical condition that would interfere with study participation. A total of 56 patients participated, and 20 of these individuals also had chronic pain.
Those with OUD and chronic pain qualified if they had pain (not related to opioid withdrawal) averaging above 3 on a 0-10 pain rating scale over the past week; additional criteria included pain for at least the past 3 months, with 10 or more days per month of pain.
Pain ratings were captured via a smartphone app that prompted participants to enter a pain rating at three random times during each day. Each evening, patients also completed a sleep diary giving information about bedtime, sleep onset latency, waking after sleep onset, and wake time for the preceding day.
A self-applied ambulatory electroencephalogram applied to the forehead was used for up to 7 consecutive nights to capture sleep continuity estimates; the device has been validated against polysomnography data in other work. Participants were given incentives to use the device, and this “yielded strong adherence,” with an average of 5 nights of use per participant, Dr. Finan said.
Patients were an average age of about 49 years, and were 75% male. African American participants made up just over half of the cohort, and 43% were white. Participants were roughly evenly divided in the type of maintenance therapy they were taking. Overall, 39% of participants had a positive urine toxicology screen.
For patients with chronic pain, 45% of all momentary pain reports had a pain score over zero, with a mean of 32 days of pain. Looking at the data another way, 58% of all patient-days had at least one momentary report of pain greater than zero, said Dr. Finan. On average, participants recorded a pain score of 2.27.
Brief Pain Inventory scores at baseline showed a mean severity of 5, and a pain interference score of 5.07.
Participants with OUD and chronic pain did not differ across any EEG-recorded sleep measures, compared with those with OUD alone. However, subjective reports of sleep were actually better overall for those with chronic pain than the objective EEG reports. The EEG recordings captured an average of 9.11 minutes more of waking after sleep onset (P less than .001). Also, total sleep time was 10.37 minutes shorter as recorded by the EEG than by self-report (P less than .001). Overall sleep efficiency was also worse by 5.96 minutes according to the EEG, compared with self-report (P less than .001).
“Sleep is objectively poor but subjectively ‘normal’ and variable in opioid use disorder patients,” Dr. Finan said. In aggregate, however, neither diary-based subjective nor EEG-based objective sleep measures differed between those with and without chronic pain in the research cohort. This phenomenon of sleep efficiency being self-reported as higher than objective measures capture sleep has also been seen in those newly abstinent from cocaine, Dr. Finan said, adding that it’s possible individuals with substance use disorder who are new to treatment simply feel better than they have in some time along many dimensions, with sleep being one such domain.
Pain on a given day didn’t predict poor sleep on that night, except that sleep onset took slightly longer (P = .01), said Dr. Finan. He noted that “there was no substantive effect on other sleep continuity parameters.”
Looking at how negative affect mediated craving for heroin, Dr. Finan and colleagues found that negative affect–related craving was significantly greater for those with chronic pain (P less than .001). Unlike findings in patients without OUD, having disrupted sleep continuity was more associated with increased daily negative affect, rather than decreased positive affect. And this increased negative affect was associated with heroin cravings, said Dr. Finan. “In the past few years, we’ve seen quite a few studies that have found some abnormalities in the reward system in patients with chronic pain.” Whether poor sleep is a mediator of these abnormalities deserves further study.
The study was supported by the National Institutes of Health. Dr. Finan reported no outside sources of funding.