Self-reported sleep duration associated with distraction analgesia, hyperemia, and secondary hyperalgesia in the heat-capsaicin nociceptive model

Abstract

Although sleep deprivation is known to heighten pain sensitivity, the mechanisms by which sleep modifies nociception are largely unknown. Few studies of sleep-pain interactions have utilized quantitative sensory testing models that implicate specific underlying physiologic mechanisms. One possibility, which is beginning to receive attention, is that differences in sleep may alter the analgesic effects of distraction. We utilized the heat-capsaicin nociceptive model to examine whether self-reported habitual sleep duration is associated with distraction analgesia, the degree of secondary hyperalgesia and skin flare, markers implicating both central and peripheral processes that heighten pain. Twenty-eight healthy participants completed three experimental sessions in a randomized within subjects design. In the pain only condition, pain was induced for approximately 70-min via application of heat and capsaicin to the dorsum of the non-dominant hand. Verbal pain ratings were obtained at regular intervals. In the distraction condition, identical procedures were followed, but during heat-capsaicin pain, subjects played a series of video games. The third session involved assessing performance on the video games (no capsaicin). Participants indicated their normal self-reported habitual sleep duration over the past month. Individuals who slept less than 6.5 h/night in the month prior to the study experienced significantly less behavioral analgesia, increased skin flare and augmented secondary hyperalgesia. These findings suggest that reduced sleep time is associated with diminished analgesic benefits from distraction and/or individuals obtaining less sleep have a reduced ability to disengage from pain-related sensations. The secondary hyperalgesia finding may implicate central involvement, whereas enhanced skin flare response suggests that sleep duration may also impact peripheral inflammatory mechanisms.

Figure 1

Pain intensity ratings for the Pain Alone and Pain w/Distraction sessions for individuals sleeping more and less than 6.5 hours/night; error bars represent standard error.

Figure 2

Percent change from Pain Alone to Pain + Distraction ratings for individuals sleeping more and less than 6.5 hours/night (calculated by subtracting pain rating under distraction from the pain alone condition, divided by pain alone, times 100: higher change indicates greater analgesic effect); error bars represent standard error.

Figure 3

Mean Flare and Secondary Hyperalgesia measurements (in mm²) for individuals sleeping more and less than 6.5 hours/night; error bars represent standard error.