The influence of age on the variability of blood pressure and heart rate responses to head-up tilt

1. The aim of this study was to establish the effect of age on the variability of blood pressure and heart rate responses to a 60 degrees head-up tilt. For this purpose, 10 head-up tilts were performed in each of 11 healthy young and 11 healthy elderly subjects under standardized conditions. Blood pressure and heart rate were measured continuously by a non-invasive method (Fin-a-pres). 2. There was a high intra-individual variability in responses which did not differ statistically between both age-groups except for the heart rate which was lower in the young subjects. This high variability in responses could not be explained by the state of hydration nor by the level of basal blood pressure. 3. In elderly, as compared to young subjects, we found less increase in diastolic blood pressure and heart rate, comparable increase in mean arterial pressure and an increase in systolic blood pressure (with no change in the young subjects). 4. It is concluded that the response of blood pressure after head-up tilt shows a great intra-individual variability, which is not age dependent. The unexpected increase of systolic blood pressure in the elderly might be related to an age-dependent increase of venous vasoconstriction in the lower extremities in response to the head-up tilt. However, an age dependent overshoot of pulse pressure in response to peripheral vasoconstriction, as measured by Fin-a-pres, cannot be excluded.