Pain tolerance as a predictor of outcome following multidisciplinary treatment for chronic pain: differential effects as a function of sex.

Sex-related differences in the experience of clinical and experimental pain have been widely reported. Females are at elevated risk for developing several chronic pain conditions and women demonstrate greater sensitivity to noxious stimulation in the laboratory. However, relationships between responses to experimental noxious stimuli and the experience of clinical pain have not been well characterized. One previous study of healthy adults indicated that pain threshold and tolerance were associated with clinical pain among women but not men (i.e. females with lower pain threshold and tolerance reported more clinical pain). In the present investigation, relationships between pain tolerance and outcomes of treatment for chronic pain were evaluated in a sex-dependent manner. Ischemic pain tolerance was assessed prior to treatment in 171 chronic pain patients completing a pain management program. Outcomes were measured as changes in pain severity, affect, and pain-related disability. Over the course of treatment, women demonstrated greater improvement in pain-related disability while men showed more reduction in pain. Ischemic pain tolerance was related to outcome in a sex-specific fashion. Women with higher pain tolerances showed greater improvement in pain, more reduction in pain-related interference, and more increases in activity level than women with lower pain tolerances. In contrast, pain tolerance was not associated with positive treatment outcomes among men. These results indicate that experimental pain responses may be most clinically relevant for women, and that sex differences may exist in the determinants of pain-treatment outcomes.