Transfer function analysis of gender-related differences in cerebral autoregulation.

Effects of gender in cardiovascular regulation are widely investigated, however differences in cerebral autoregulation (CA) between genders remains less explored. In the present study, we used spectral analysis to analyze differences in cerebral autoregulation between 10 men and 10 age-matched women. Subjects rested in a supine position (20 min) and then were passively tilted to a 70-degree head up tilt position (30 min). During the first 10 min of supine they breathed only room air (Supine Control) while during the second 10 min of supine they breathed room air or room air plus 5% CO2 in a Pseudo Random Binary Sequence (PRBS) (Supine PRBS). During the first 10 min of tilt, subjects breathed room air or room air plus 5% CO2 switched in a PRBS (Tilt PRBS). For the remaining 20 min of tilt, they breathed only room air (Tilt Control). Blood pressure (BP) and cerebral blood flow velocity (CBFV) were non-invasively recorded using Finapres and Transcranial Doppler. Coherence and transfer function between mean BP and mean CBFV were estimated. During Supine Control, women had higher coherence (p < 0.05) and transfer function gain (p < 0.01) within 0.03-0.10 Hz and 0.22-0.31 Hz than men. During tilt, coherence within 0.05-0.26 Hz were higher in men than in women (P < 0.02). Although the reasons for these gender-related differences in cerebral autoregulation remain unclear, our results suggest that in investigating cerebral autoregulation, gender may need to be considered as a factor.