Gender related differences in the cardiovascular responses to upright tilt in normal subjects

The heart rate and blood pressure responses to head-up tilt of 80 degrees was studied in 20 normal men and 21 normal women aged 20-50 years (mean age 31.1 ± 7.1 years). The heart rate increase in females during tilt was 73% that of males, whereas the increase in diastolic pressure during tilt was 29% of males. Expressed in relation to values obtained supine, heart rate increases on average 30.3% in men as compared to 21.5% in women whereas diastolic pressure increases by 15.2% in men as compared to an increase of only 4.3% in women. The data indicates that the cardiovascular response of normal females to upright tilt differs significantly from that of normal males. This attenuated responsiveness to ortho-stasis in women relative to men may predispose women to postural insufficiency and may account for the predominance of symptomatic women with clinically mild dysautonomia.