Cerebral autoregulation across the menstrual cycle in eumenorrheic women. Issue 9 (6th May 2022) - Korad, Stephanie
Abstract: There is emerging evidence that ovarian hormones play a significant role in the lower stroke incidence observed in pre‐menopausal women compared with men. However, the role of ovarian hormones in cerebrovascular regulation remains to be elucidated. We examined the blood pressure‐cerebral blood flow relationship (cerebral autoregulation) across the menstrual cycle in eumenorrheic women ( n = 12; mean ± SD: age, 31 ± 7 years). Participants completed sit‐to‐stand and Valsalva maneuvers (VM, mouth pressure of 40 mmHg for 15 s) during the early follicular (EF), late follicular (LF), and mid‐luteal (ML) menstrual cycle phases, confirmed by serum measurement of progesterone and 17β‐estradiol. Middle cerebral artery blood velocity (MCAv), arterial blood pressure and partial pressure of end‐tidal carbon dioxide were measured. Cerebral autoregulation was assessed by transfer function analysis during spontaneous blood pressure oscillations, rate of regulation (RoR) during sit‐to‐stand maneuvers, and Tieck's autoregulatory index during VM phases II and IV (AI‐II and AI‐IV, respectively). Resting mean MCAv (MCAvmean ), blood pressure, and cerebral autoregulation were unchanged across the menstrual cycle (all p > 0.12). RoR tended to be different (EF, 0.25 ± 0.06; LF; 0.19 ± 0.04; ML, 0.18 ± 0.12 sec −1 ; p = 0.07) and demonstrated a negative relationship with 17β‐estradiol (R 2 = 0.26, p = 0.02). No changes in AI‐II (EF, 1.95 ± 1.20; LF, 1.67 ± 0.77 and ML, 1.20 ± 0.55) or AI‐IV (EF, 1.35 ± 0.21; LF, 1.27 ± 0.26 and ML, 1.20 ± 0.2) were observed ( p = 0.25 and 0.37, respectively). Although, a significant interaction effect ( p = 0.02) was observed for the VM MCAvmean response. These data indicate that the menstrual cycle has limited impact on cerebrovascular autoregulation, but individual differences should be considered. Abstract : We describe cerebral autoregulation in eumenorrheic women in the early and late follicular, and mid‐luteal phases of the menstrual cycle. The rate of regulation following repeated sit‐to‐stand maneuvers was correlated with plasma estrogen, with reduced regulation found in women with greater plasma estrogen. No differences in resting hemodynamic variables were observed across the menstrual cycle. These data highlight the individual variation of the cerebrovascular response to forced oscillations in blood pressure in eumenorrheic women.