Sex differences in temporal summation of pain and aftersensations following repetitive noxious mechanical stimulation

Several studies demonstrate that women are more sensitive to experimental pain than men. In addition, women exhibit greater temporal summation of heat and mechanically evoked pain. Since temporal summation of pain is centrally mediated, its greater expression in women suggests a central nociceptive hyperexcitability relative to men. The purpose of this study was to pursue this theory, by further assessing sex differences in (1) temporal summation of mechanically evoked pain, and (2) aftersensations following repetitive noxious stimulation. Sixteen series of 10 repetitive, mildly noxious, mechanical stimuli were applied to the fingers of 25 women and 25 age-matched men. The subjects rated the pain intensity and unpleasantness caused by the first, fifth and tenth stimulus in the series, as well as their aftersensations 15 s and 1 min following the end of stimulation. Data were analyzed by three-way repeated-measures analysis of variance. Pain and unpleasantness ratings increased with repetition of stimulation (P