To assess the effects of delta wave sleep interruption (DWSI) on pain thresholds and fibromyalgia-like symptoms. To examine the potential correlations between DWSI and serum insulin-like growth factor 1 (IGF-1).
Thirteen healthy volunteers were subjected to 3 consecutive nights of DWSI (Group 1). Pain thresholds were measured by dolorimetry and symptoms by visual analog scale. Six subjects not undergoing DWSI served as dolorimetry and symptom controls (Group 2). Serum IGF-1 was measured by competitive binding radioimmunoassay before and after DWSI.
No significant differences in pain thresholds as a function of condition (baseline, DWSI, recovery) or overnight change were detected between or within groups (p>0.05). Morning mean dolorimeter scores were lower than evening scores in both groups during all 3 conditions, and were lower in Group 1 than in Group 2 during DWSI. Group 1 subjects had higher composite symptom scores during DWSI (p< or =0.005), attributed largely to increases in fatigue. Serum levels of IGF-1 from Group 1 subjects showed no significant change after DWSI (p>0.05).
In our study subjects, 3 nights of DWSI caused no significant lowering of pain thresholds compared with a control group. Subjects appeared to have lower pain thresholds in the mornings, and DWSI appeared to augment this effect. Symptoms were more apparent during DWSI, but were primarily related to fatigue. IGF-1 was not altered by 3 nights of DWSI. The low levels of IGF-1 seen in patients with fibromyalgia syndrome may result from chronic rather than acute DWSI, or may be dependent on factors other than disturbances of delta wave sleep.