Twenty-four participants were randomly assigned to Sleep (N= 9) or TSD (N=15). Sleep and TSD groups did not differ with respect to female/male ratio (3/6 vs. 4/11, ns) and BMI (23.2 3.4 vs. 25.5 4.2 m2/kg, ns). The sleep group was younger than the TSD group (30.4 5.6 vs. 37.9 6.5 years, p<0.05). However, there was no correlation between the increase in PGE-M excretion or pain scores with age.
Urine output from baseline to the third experimental day in the CRC increased significantly increased in both TSD and sleep group (F[1,22]=20.84, p<0.01 for time effect), but did not differ between groups (F[1,22]=2.81, NS, for interaction effect; see top panel).
Top left: Urine output in 24h collections at baseline and 3rd day under conditions of TSD (N=15) or control sleep (N=9).
Urinary PGE-M levels showed large inter-individual differences ranging from 215 to 3553 pg/24h urine output at baseline. The lower left panel of depicts the raw data at baseline and third day of SD. The lower right panel of shows the change from baseline of log-transformed data. GLM analysis of PGE-M levels showed a significant time by group interaction effect (F[1,22]=5.42, p<0.05). This was due to a significant increase in the TSD group from baseline to third day of TSD (F[1,14]=4.97, p<0.05), while the sleep group showed a slight non-significant decrease (F[1,8]=1.60, NS). Results of GLM analysis of PGE-M levels did not change after controlling for age and for sex (F[1,21]>5.00, p<0.05).
Univariate testing with baseline as covariate showed sig. higher values in the SD group compared to the sleep group on the third day of SD (F[1,21]=5.96, p<0.05). PGE-M increased in eleven out of 15 participants increased in the TSD condition, compared to one out of nine participants in the sleep condition.
One participant in the sleep group had missing data due to computer failure, reducing sample size in the sleep group to N=8. shows the raw data of intensity ratings of spontaneous pain (averaged across all pain items, i.e. headache, muscle pain etc.). (top left panel) shows log-transformed spontaneous pain ratings presented as change from baseline and averaged across study days. GLM analysis of spontaneous pain ratings showed a significant time by group interaction effect (F[3,60]= 5.00, p<0.05). This was due do an increase of spontaneous pain in the TSD group (F[4,56]=11.46, p<0.001 for time effect), while pain ratings in the sleep group stayed stable across days (F[4,28]=0.15, NS for time effect). GLM analysis of spontaneous pain ratings controlled for age and for sex did not change results (F[3,57]>4.7, p<0.05).
Intensity ratings of spontaneous measured every 2 hours throughout the protocol. For statistical analysis, ratings were averaged across days and log-transformed (see )
Left panel: Intensity ratings of spontaneous pain (averaged across days), headache, and muscle pain significantly increased throughout three nights of TSD (N=15) compared to 8h control sleep (N=8, p<0.05 for interaction effect).
With respect to group differences at single time points (baseline taken as covariate in univariate testing), ratings were significantly higher in the TSD group compared to the sleep group starting on the first TSD night, and went back to baseline after a night of recovery sleep.
With respect to single pain items, participants in the TSD group experienced increased generalized body pain, physical discomfort, headache, stomach pain, and muscle pain compared to participants with a regular sleep schedule (all F[3,60]>4.0, p<0.05 for interaction or group effect, see middle and lower left panel in for the pain items headache and muscle pain). No significant interaction or group effects were observed for joint pain and back pain.
Change of spontaneous pain from baseline to third TSD day was 9 12 units on a 100-unit scale. Higher changes could be seen in ratings assessing unspecific pain items (i.e. generalized body pain and physical discomfort (14 17 units and 14 19 units, resp.)) than localized pain (i.e. headache, stomach pain, and muscle pain (6 12, 5 12, and 9 19 units, resp.)).
Under baseline conditions, PGE-M levels were not significantly correlated with intensity ratings of spontaneous pain (R=−.28, NS).
Change in PGE-M metabolite levels from baseline to 3rd TSD day was positively correlated with spontaneous pain (R=.52, p<0.05) and localized pain items of headache (R=.55, p<0.05), muscle pain (R=.64, p<0.05), back pain (R=.65, p<0.01), and joint pain (R=.58, p<0.05), indicating that sleep deprivation-induced increase in PGE-M is associated with an increase in spontaneous pain complaints (see right panel in ).