Local versus distal acupoint low-level light therapy for pain relief in primary dysmenorrhea: protocol for a...

Primary dysmenorrhea (PD) is a common gynecological condition affecting a substantial proportion of women of reproductive age. Non-steroidal anti-inflammatory drugs often provide incomplete pain relief and may be associated with adverse effects (AEs), highlighting the need for low-risk, non-pharmacological alternatives. Low-level light therapy (LLLT) has emerged as a promising non-invasive modality for pain management; however, the comparative effects of LLLT applied to local versus distal acupoints remain unclear.

This is a single-center, prospective, randomized, assessor- and statistician-blinded, parallel-group pilot study. A total of 60 women with moderate-to-severe PD will be randomized to receive LLLT at either local or distal acupoints. Interventions will be administered once daily for 7 consecutive days prior to menstruation across three menstrual cycles. Pain intensity will be assessed using the visual analog scale (VAS). Multimodal biosignals, such as electrocardiography, electromyography, electrodermal activity, photoplethysmography, respiration, and skin temperature, will be recorded to explore physiological responses to treatment. The primary outcome is the change from baseline in VAS measured at the scheduled post-menstrual visit occurring within 3 days after the onset of menstruation, assessed across three menstrual cycles. The secondary outcomes include biosignal changes, patient-reported outcomes, and the Patient Global Impression of Change.

To the best of our knowledge, this will be one of the first randomized studies to directly compare LLLT applied to local and distal acupoints in patients with PD. As a comparative pilot study, it is not designed to establish definitive efficacy but to explore differences between stimulation strategies and to generate preliminary data for future confirmatory studies.

https://cris.nih.go.kr/cris/search/detailSearch.do?seq=30497&sea. This study has been registered with the Clinical Research Information Service, identifier KCT0010827 (registration date: 29 July 2025).