Experimentally induced pain perception in men and women in the morning and evening

The literature regarding whether or not there are diurnal differences in pain perception in men and women is equivocal. The purpose of this study was to examine the influence of time of day on experimentally induced pain threshold in men and women. A secondary purpose was to measure selected psychological and physiological responses. Pressure (3000 gm force) was applied to the middle digit of the left forefinger for 2-min with the Forgione-Barber pain stimulator. Twenty-nine volunteers (women = 14; men = 15) completed two randomly assigned sessions between 6.00-8.00 in the AM and PM. Selected psychological variables (STAI,POMS) and physiological variables (BP, HR, TEMP) were assessed before application of the pressure stimulus. Data were analyzed with a 2x2 ANOVA. Results indicated that men had significantly higher (p<.05) systolic blood pressure and pain thresholds than women however, there was not a significant time of day effect for pain threshold. Significant time of day effects (p<.05) were found for systolic blood pressure and tympanic temperature. Heart rate, and tympanic temperature were found to be significantly higher (p<.05) in women in comparison to men. It is concluded that pain threshold did not differ in the AM and PM. Furthermore, men were found to have higher pain thresholds compared to the women.