The effect of two nights of partial sleep restriction on objective and subjective pain measurements

Abstract

Introduction The exact nature of the relationship between sleep reduction and pain is still not known and further clinical studies are needed to elucidate the relationship between sleep and pain further. Materials and methods Students were recruited through intranet advertisement at our University and Hospital. Of the 80 students who responded to the invitation, 34 (mean age 22.9) were included in the present paper and randomly assigned to either sleep deprivation (SD) or habitual sleep (HS) subgroups. They had repeated neurophysiological examinations with two nights of sleep deprivation or habitual sleep in between. Pain responses were measured with laser evoked potentials (LEP), thermal threshold and suprathreshold test. Repeated measures ANOVA was used to evaluate the possible interaction between sleep deprivation and pain measures. The effect of sleep deprivation was also investigated using two additional categorizations; as actual PSG-recorded REM sleep and SWS (median splits). The difference between N2P2 amplitude, thermal pain threshold and pain ratings were compared between sleep categorization subgroups with Mann-Whitney U-test. The difference between baseline and follow-up values within the sleep groups where investigated with the Paired T-test. Results RANOVA revealed a significant interaction between day x sleep for the N2P2 amplitude (p = 0.02) because amplitude decreased in the 4-h group (p = 0.03) while it was more stable in the 9-h group. We also found a significant interaction between day  ×  sleep for cold pain threshold at thenar (p = 0.003), and further analyses with the Paired T-test demonstrated that cold pain threshold was significantly decreased after sleep deprivation (p = 0.02), while no change was observed within the habitual sleep group. Conclusion Partial sleep deprivation has minor, but significant effects on objective and subjective pain measurements. Subject randomized to four hours sleep had a smaller LEP N2P2- amplitude, no change in suprathreshold pain ratings and a lower threshold for cold pain the at day 3, compared to subjects randomized to nine hours sleep. Acknowledgements The authors are most grateful to the subjects of the present study for their participation.