This study examined the specific physiological responses of women with primary dysmenorrhea during the severely painful menstrual (days 1-2 of menstruation) and the non-painful follicular phases (days 5-8 after the onset of menstruation). Subjects consisted of 10 severe primary dysmenorrheic (Group P) and 10 non-dysmenorrheic women (Group C) with regular menstrual cycles. However, only 9 out of 10 and 8 out of 10 subjects of Groups P and C participated during the follicular phase. Physiological measures were taken in a resting state for 60 min. In the menstrual phase, the pain ratings and secretory immunoglobulin A (s-IgA) concentrations of Group P were significantly higher than those of Group C, with relatively significant decreases in the leg-skin temperature in the former as well. In addition, the systolic (SBP) and diastolic blood pressure (DBP) at 45 min after rest in Group P were significantly higher than those found in Group C. These reactions strongly suggest activation of the sympathetic-adrenal-medullary axis (SAM axis) by painful stress. Furthermore, the low-frequency (LF) component of the SBP variability (SBPV) was significantly higher in Group P than Group C, even during the follicular phase. These findings imply that Group P may well have elevated activities of the SAM axis throughout the whole menstrual cycle. As such, it suggests that dysmenorrheic women may be affected by certain stressors other than pain per se and pain-derived emotions throughout the whole menstrual cycle. The findings also indicate that women with dysmenorrhea have more sensitive responses to the SAM system than non-dysmenorrheic women during stress. Moreover, the high-frequency (HF) component of heart rate variability (HRV), or the index for the vagus nerve activity, displayed a consistently higher value in Group P than C. It is postulated that the human body may have responded to pain in an attempt to maintain the homeostatic state by enhancing vagus nerve activity.

Correlation of unpleasantness and electroencephalography (EEG)-based responses induced by persistent mechanical/dry stimulation and acute wet stimulation via wearing sanitary napkins (SN) was investigated in the present study. Mesh and nonwoven SN were employed, and the effects were studied during the follicular and menstrual phases. The mesh SN characteristically displayed a higher textural surface-roughness. The results in the follicular phase revealed no change in EEG responses to nonwoven SN-induced persistent mechanical stimulation, while the same dry stimulus induced significant increases in alpha2 and beta activities in the bilateral frontal areas accompanied by markedly exacerbated unpleasantness with mesh compared with nonwoven SN. The present result with SN application confirms the previous finding that unpleasantness is well correlated with EEG responses of bilateral frontal areas. Interestingly, although the alpha2 activities were enhanced more with mesh than nonwoven SN during the menstrual phase, unpleasantness between the two textural materials was not different. Moreover, it is suggested that acute unpleasantness induced by wet stimulation is related with elevated EEG responses in the left hemisphere. These data suggest that subjective evaluation of effects of physical stimulation on the human body may not be adequately reliable, and objective assessment of physiological activities with EEG is warranted.

This study investigated the physiological and psychological effects of sanitary napkins (SN) on women in hemorrhage treatment during the menstrual phase. Mesh and non-woven napkins were employed, and the effects were studied during the follicular and menstrual phases; mesh SN presented a higher textural surface-roughness. In both phases, the increases in systolic and diastolic blood pressure were significantly dependent on the application intervals. The lowfrequency component of systolic blood pressure variability significantly increased, while the salivary secretion rate decreased with the use of mesh SN during the follicular phase compared with non-woven SN. In addition, the heart rate during the menstrual phase significantly increased in subjects after the replacement of mesh SN compared with non-woven SN. In cases of wearing the unpleasant mesh SN, electroencephalography (EEG) manifested bilateral enhancements in b and a2 waves in the frontal areas increased arousal level during both phases. From the above findings, napkin use increased physiological loading and wearing napkins with higher textural surface-roughness tended to increase activities of the autonomic nervous system and brain arousal level.