Reproducibility Of The Impact Of Menstrual Phase On Arterial Stiffness Over Two Consecutive Menstrual Cycles

Chronic increases in arterial stiffness are associated with increased risk of cardiovascular disease. Estrogen (E2), the primary female sex hormone, has been found to have cardioprotective effects, with several but not all, studies reporting a reduction in arterial stiffness in the late follicular (high E2; LF) phase compared to the early follicular (low E2; EF) phase of the menstrual cycle. Individual heterogeneity in the impact of phase on arterial stiffness and the consistency of these responses across consecutive cycles has yet to be explored. PURPOSE: to determine the impact of menstrual phase E2 fluctuations on arterial stiffness over two consecutive cycles. METHODS: 13 premenopausal women completed 4 experimental visits over 2 menstrual cycles (EFvisit 1, LFvisit 2, EFvisit 3, LFvisit 4). Central (CF) and peripheral (FF) PWV were measured twice during each visit using arterial tonometry. Participants were classified as positive, negative or non-responders, wherein positive responders experienced a reduction in PWV from EF to LF and negative responders experienced an increase in PWV from EF to LF that was greater than 2*typical error. RESULTS: At the group level, CF PWV did not differ between phases (p=0.11) or cycles (p=0.18; EFvisit 1=5.8±0.8, LFvisit 2=5.6±0.5, EFvisit 3=5.9±0.6, LFvisit 4=5.8±0.7). Likewise, FF PWV did not differ between phases (p=0.979) or cycles (p=0.58; EFvisit 1=8.1±1.0, LFvisit 2=8.1±1.1, EFvisit 3=7.9±1.4, LFvisit 4=8.0±1.3). Phase changes in E2 were not associated with phase changes in PWV in cycle 1 (CF: r=0.38, p=0.20; FF: r=0.11, p=0.73) or cycle 2 (FF: r=0.38, p=0.36). Classification of individuals as responders or non-responders revealed that no participants were consistently positive or negative responders for both cycles. CONCLUSION: At the group level, arterial stiffness was not impacted by menstrual phase over two cycles. Individual changes in arterial stiffness were inconsistent, with phase changes in cycle 1 not reflecting phase changes in cycle 2. Variability in phase changes in arterial stiffness does not appear to be driven by inter-individual differences in E2 fluctuation across phase. Future research is needed to investigate the mechanisms resulting in inter-individual variability in arterial stiffness and inconsistency between cycles. Funded by NSERC