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 orthostasis in women relative to men may predispose women to postural insufficiency and may account for the predominance of symptomatic women with clinically mild dysautonomia.