Abstract
BACKGROUND: Primary dysmenorrhea is fundamentally driven by uterine ischemia resulting from excessive vascular resistance. While acupuncture is theorized to improve perfusion, high-quality evidence controlling for pharmacological confounders is limited. This study aimed to evaluate the hemodynamic effects and longitudinal analgesic efficacy of the "Regulating Ren and Unblocking Du" acupuncture protocol. METHODS: This retrospective cohort study analyzed data from 286 patients treated between 2020 and 2024. To minimize selection bias, a 1:1 Propensity Score Matching (PSM) algorithm was applied to balance baseline covariates, including medication regimen (NSAIDs vs. hormonal therapy), disease severity, and age at menarche. The final matched cohort included 158 patients (79 pairs). The intervention group received acupuncture plus conventional medication, while the control group received medication alone. Primary outcomes included uterine artery Doppler indices (Pulsatility Index [PI], Resistance Index [RI], S/D ratio) and Visual Analogue Scale (VAS) pain scores assessed at 1, 3, and 6 months. RESULTS: Post-treatment, the acupuncture group exhibited significantly lower vascular resistance compared to controls, with a mean difference of -0.54 (95% CI: -0.66 to -0.42) for PI and -1.7 for the S/D ratio (p < 0.001). Clinically, acupuncture provided superior rapid analgesia; at 1 month, VAS scores were significantly lower in the intervention group compared to controls (p < 0.001). This advantage persisted at 3 months but converged by 6 months (p = 0.32), indicating a diminishing differential effect over time. Subgroup analyses revealed enhanced efficacy in patients aged <30 years or with a disease duration <5 years. Minor adverse events occurred in 6.3% of acupuncture recipients. CONCLUSION: After rigorously adjusting for confounders, acupuncture was associated with reduced uterine arterial resistance. Clinically, it offers a distinct "window of opportunity" for rapid symptom control in the early treatment phase, particularly for younger patients.