Total Sleep Deprivation and Pain Perception during Cold Noxious Stimuli in Humans.

BACKGROUND AND AIMS: A substantial portion of the population suffers from chronic pain leading to significant health care costs and lost productivity. Loss of sleep duration and quality are widely reported in patients suffering from a variety of acute or chronic pain conditions. Conversely, sleep loss has been known to elevate pain perception; thus a potential bi-directional relationship exists between sleep deprivation and pain. To date, the majority of studies examining the relationship between experimentally induced pain and sleep loss have focused on the measurement of pain threshold . Additionally, despite evidence of sex differences in ratings of perceived pain, previous studies examining pain following sleep loss have not probed for sex differences. We examined the effects of 24-hour total sleep deprivation (TSD) on perceived pain during a 2-minute cold pressor test (CPT). We hypothesized that TSD would augment perceived pain and that women would demonstrate an elevated pain response compared to men.

METHODS: Testing was carried out in 14 men and 13 women. All subjects reported to be nonsmokers with no history of cardiovascular disease, autonomic dysfunction, asthma, or diabetes. All female subjects were free of oral contraceptive use, and were tested during the early follicular phase of the menstrual cycle. Trial order was randomized and testing sessions (Normal sleep (NS) and TSD) were separated by approximately one month. Subjects immersed their left hand, up to the wrist, in an ice water bath (~1°C), and perceived pain was recorded every 15 seconds from a modified Borg scale (6-20 arbitrary units a.u.).

RESULTS: Perceived pain responses during CPT were augmented following TSD (Δ1.2 a.u.; time × condition, p<0.05). The augmented pain response following TSD was noted when perceived pain was expressed as mean (NS Δ7.0±0.5 vs. TSD Δ8.2±0.5 a.u.; p<0.05) or peak (NS Δ8.9±0.6 vs. TSD Δ10.2±0.5 a.u.; p<0.05) perceived pain. The effects of TSD on perceived pain were similar in both men and women (condition × time × sex, p>0.05).

CONCLUSIONS AND IMPLICATIONS: We conclude that TSD significantly augments perceived pain during CPT, but this response was not sex dependent. These findings support emerging evidence that adequate sleep represents a relevant, and cost effective, preventative/therapeutic strategy to reduce self-perceived pain in both men and women.