CARDIOVASCULAR-RESPONSES TO POSTURAL CHANGES - DIFFERENCES WITH AGE FOR WOMEN AND MEN

The cardiovascular responses to postural change, and how they are affe cted by aging, are inadequately described in women. Therefore, the aut hors examined the influence of age and sex on the responses of blood p ressure, cardiac output, heart rate, and other variables to change in posture. Measurements were made after 10 minutes each in the supine, s eated, and standing positions in 22 men and 25 women who ranged in age from 21 to 59 years. Several variables differed, both by sex and by a ge, when subjects were supine. On rising, subjects' diastolic and mean arterial pressures, heart rate, total peripheral resistance (TPR), an d thoracic impedance increased; cardiac output, stroke volume, and mea n stroke ejection rate decreased; and changes in all variables, except heart rate, were greater from supine to sitting than sitting to stand ing. The increase in heart rate was greater in the younger subjects, a nd increases in TPR and thoracic impedance were greater in the older s ubjects. Stroke Volume decreased less, and TPR and thoracic impedance increased more, in the women than in the men. The increase in TPR was particularly pronounced in the older women. These studies show that th e cardiovascular responses to standing differ, in some respects, betwe en the sexes and with age. The authors suggest that the sex difference s are, in part, related to greater decrease of thoracic blood volume w ith standing in women than in men, and that the age differences result , in part, from decreased responsiveness of the high-pressure barorece ptor system.