The effects of controlled delta sleep deprivation on experimental pain in healthy subjects

Objectives: The interaction between sleep and pain is important in patients suffering from rheumatic illness. Not only can pain disturb sleep, but alt erations in the deeper sleep stages induced by the disease process may have the potential to decrease the pain threshold. Previous studies however, ha ve shown diverging results. In the current experiment we studied the effect s of deep sleep deprivation using a standardized, computer-assisted system on subjective symptoms and pain elicited by different experimental modaliti es. Methods: Ten healthy males, mean age 22.7 years, were subjected to deprivat ion of the deeper sleep stages for three nights. Following a baseline recor ding, sleep was analyzed in 2 s segments with on-line frequency analysis. I f any 30 s epoch contained more than seven 2 s segments dominated by low fr equency content corresponding to deep sleep, the sleep was disturbed by an acoustic stimulus. The amount of delta power was computed in sleep stages n on-rapid-eye-movement [NREM]2-4. Subjects rated different questions regardi ng their feeling of pain, discomfort and psychological complaints twice a d ay during the experiment. Experimental pain was assessed with thermal [heat and cold presser] and electrical stimuli as well as pressure pain threshol ds in different areas of the body. Results: The first night of deep sleep deprivation resulted in a reduction in delta power to 39.3 and 10.5% of the baseline in stages NREM3 and 4, res pectively [P = 0.005, P = 0.015]. In five subjects the delta power deprivat ion in stages NREM3 + 4 was 62.2% of baseline in the second deprivation nig ht [P = 0.043]. No consistent changes however, were found for the subjectiv e ratings or the experimental pain assessments following the first deprivat ion night. For the five subjects who were sufficiently deprived for deep sl eep in two nights, the same findings as above were seen following both nigh ts. Conclusion: Controlled delta power deprivation during sleep did not result in pain in healthy, young males. Although sleep disturbances may interact w ith pain and other daytime symptoms, we believe that other factors such as premorbid genetic constitution, age, sex, and several external factors are necessary before sleep disturbances per se are able to induce musculoskelet al symptoms.