Patients with CNCP frequently experience concomitant sleep-related problems and there has been controversy on whether opioids have a beneficial or deleterious effect on sleep quality, duration and efficiency. The aim was to evaluate sleep problems in opioid naïve CNCP patients, before and after opioid titration, analyzing the influence of OPRM1 gene variants. A prospective, cohort, observational study, at the Pain Unit of the Alicante University General Hospital. Pain and Medical Outcomes Study Sleep questionnaire (MOS-Sleep) were assessed at baseline and 3 months after opioid titration in 231 opioid naïve CNCP patients. Sleep data was compared with a matched-control group without CNCP (n = 64). Morphine equivalent daily doses (MEDD), adverse events, and drugs prescribed for pain were also registered. OPRM1 (c.118G>A, rs1799971) polymorphism was analyzed by RT-PCR. Ethics Committee approved the study and results were analyzed by R software. After 3 months of opioid titration, patients with CNCP (63 ± 14 years, 64% female, VAS 74 ± 17 mm) significantly decreased pain intensity, anxiety and depression, and increased quality of life. Sleep problems were significantly more frequent in females. Age, quality of life, anxiety, and depression all influenced sleep disturbances and problems indices, which were significantly different from the control group. Furthermore, the OPRM1 118-GG genotype was also associated with significantly lower sleep adequacy, and more sleep problems. Opioids decreased CNCP severity, improving patients' psychological areas, and quality of life. However, patients with OPRM1 118-GG genotype indicated an increase in sleep problems and worsening sleep pattern while taking opioids.

SLEEP-RELATED PROBLEMS IN CHRONIC PAIN PATIENTS TREATED WITH OPIOIDS