Low-level Light Therapy for Primary Dysmenorrhea

Study design: This was a prospective, randomized, double-blind, placebo-controlled, multi-centered trial carried out at two university hospitals. This clinical trial was approved by the Korea Food and Drug Administration and the Institutional Review Boards of the two hospitals.

Study process:

All patients gave informed written consent after being informed of the details of the study. Participants were permitted to take analgesics when severe or difficult to control pain occurred. Participants were randomized into either the LLLT or placebo control groups at the third visit. All participants underwent demographic and history taking, a physical examination, an obstetrics and gynecology examination, ultrasound, and laboratory tests. All participants were educated on how to use the device by demonstration and a picture-guided user manual.

During the second visit, the participants conducted a self-evaluation of pain intensity and quality of life after the next menstruation started (pre-treatment score) using the VAS and EQ-5D questionnaire. The third visit occurred at least 5-7 days from the date of the next menstruation, and a clinical primary nurse described how to use the medical equipment and devices when they were at home. All subjects were to perform the LLLT 20 min/day for 5 days from the start of menstruation. Within 3 days after menstruation started the subjects self-assessed their pain using the VAS after treatment (first post-treatment score). Subjects carried out the self-treatment in the same way at home 5-7 days before the start of their next period and then visited the hospital for the fifth time to record their pain on the VAS (second post-treatment score). As before, self-therapy was performed 5-7 days before the next menstruation started. The sixth visit occurred within 1-3 days after menstruation began, just as before, and all subjects performed the self-evaluation (third post-treatment score) using the EQ-5D questionnaire and VAS for menstrual pain intensity.

Statistical analysis:

All data are summarized as means ± standard deviation or as numbers with proportions. A p < 0.05 was considered to indicate significance. We decided that the therapeutic effect would be a > 30% reduction in the VAS value after treatment. The statistical analysis was conducted using the VAS assessment score after the third treatment as the primary endpoint. We used an independent t-test to evaluate differences in each group between VAS pain scores measured after the third treatment and baseline values. The influence of variance in each group after pre-treatment, primary treatment, secondary treatment, and tertiary treatment were verified through repeated-measures analysis of variance (ANOVA). We analyzed the differences in the EQ-5D in each group using analysis of covariance (ANCOVA). Age was considered a covariate. Any differences between the groups for the use of painkillers were analyzed by Fisher's exact test. If there was any difference in the use of pain killers between groups, the influence of pain killer use was closely checked by ANCOVA. A per-protocol (PP) analysis was used in our clinical trial to assess efficacy and safety.