Impact of the menstrual cycle on peripheral vascular function in premenopausal women: systematic review and meta-analysis.

Fluctuations in endogenous hormones estrogen and progesterone during the menstrual cycle may offer vasoprotection for endothelial and smooth muscle (VSM) function. While numerous studies have been published, the results are conflicting, leaving our understanding of the impact of the menstrual cycle on vascular function unclear. The purpose of this systematic review and meta-analysis was to consolidate available research exploring the role of the menstrual cycle on peripheral vascular function. A systematic search of MEDLINE, Web of Science, and EMBASE was performed for articles evaluating peripheral endothelial and VSM function across the natural menstrual cycle: early follicular (EF) phase versus late follicular (LF), early luteal, mid luteal, or late luteal. A meta-analysis examined the effect of the menstrual cycle on the standardized mean difference (SMD) of the outcome measures. Analysis from 30 studies (n = 1,363 women) observed a "very low" certainty of evidence that endothelial function increased in the LF phase (SMD: 0.45, P = 0.0001), with differences observed in the macrovasculature but not in the microvasculature (SMD: 0.57, P = 0.0003, I2 = 84%; SMD: 0.21, P = 0.17, I2 = 34%, respectively). However, these results are partially explained by differences in flow-mediated dilation [e.g., discrete (SMD: 0.86, P = 0.001) vs. continuous peak diameter assessment (SMD: 0.25, P = 0.30)] and/or menstrual cycle phase methodologies. There was a "very low" certainty that endothelial function was largely unchanged in the luteal phases, and VSM was unchanged across the cycle. The menstrual cycle appears to have a small effect on macrovascular endothelial function but not on microvascular or VSM function; however, these results can be partially attributed to methodological differences.