Actigraphy-Based Evaluation of Sleep Improvement during Treatment of Chronic Neuropathic Pain with Transdermal Fentanyl

Background: The association between chronic pain and sleep disorders is well established. Studies indicate that painful stimuli arouse, delay, and diminish the quality of sleep. Sleep deprivation and disruption, in itself, may also elicit hyperalgesia and hypersensitization to external stimuli. The establishment of this vicious cycle in chronic pain may perpetuate the disorder and its comorbidities. Aim: To examine the effects of chronic pain on sleep using objective measures, and determine if reduction in pain is associated with parallel improvements in sleep for patients with chronic neuropathic pain. Methods: Forty patients with chronic neuropathic pain (postamputation pain, peripheral neuropathy, CRPS) were followed over a sixteen-week period. Pain intensity and activity during sleep was measured using an Actiwatch that subjects were asked to wear continuously. After 2-wk baseline measurements, transdermal fentanyl was titrated to effect over the subsequent six-weeks and patients were followed for an eight-week maintenance period. The actigraph tracings were processed to determine wake-after-sleep-onset (WASO), sleep fragmentation (a measure of sleep quality) and number of wake bouts. Pain relief was defined by at least a 50% improvement in pain score. Data were censored at the last available timepoint. Results: Of the forty eligible patients, twenty-five completed the study. Baseline and treatment phase actigraphy data were available for 20 subjects. Change from baseline in wake after sleep onset was improved in the pain relief group (improvement of 60% over the no pain relief group, p<0.05). Sleep fragmentation and number of wake bouts were also statistically significantly improved in the pain relief group (p<0.05). Conclusion: Patients who have relief of chronic neuropathic pain treated with transdermal fentanyl have an improvement in sleep quality as measured by actigraphy. Actigraphy may be a useful tool to study sleep disturbances in chronic pain patients and examine the effects of pain therapies on sleep.