Changes of heat pain sensitivity during the menstrual cycle in Japanese young adults: a randomized trial

The aim of this study was to compare pain sensitivity between the follicular and luteal phases of the menstrual cycle in Japanese young adults. Fifteen females participat ed in this randomized control trial with crossover design. The pain threshold (defined as the temperature when the subject started to feel pain) was measured using a heat pain stimulator on the short flexor muscle of the thumb. For each subject, the stimulus was performed 10 times, alternating between the right and left hand. Pain reactivity was evaluated using a self–identified threshold of heat pain, salivary alpha amylase, emotional evaluation using a profile of mood states and visual analog scale scores. After comparative analysis, we found that pain threshold under the follicular phase was significantly increased compared to that under the luteal phase, indicating that the menstrual cycle would influence the severity of pain perception. Pain sensitivity under the luteal phase is more sensitive to nociceptive stimuli than those under the follicular phase. We therefore need to conduct pain management with paying heed to the menstrual cycle. Additionally, young women in reproductive–age should be more protective in pain management during the luteal phase of their menstrual cycle. This study was conducted during the follicular and luteal phases of the menstrual cycle. Heat pain stimuli were performed a total 10 times on the right and left hands, alternately. Moreover, subjects rested for 2 min between each heat pain stimulus to avoid any carryover effects and habituation to the heat pain stimulus. POMS: Profile of Mood States; VAS: Visual analogue scale; hand;