Ageing and cardiovascular responses to head-up tilt in healthy subjects.

Objective: Ageing is associated with increased postural blood pressure changes and attenuated cardiovascular reactivity. As the background of these changes remains uncertain, we examined arterial stiffness, cardiac function and vascular resistance in healthy subjects in supine position and during orthostatic challenge.

Methods: Haemodynamics of 179 normotensive subjects (109 female and 70 male, 21-59 years) were examined using continuous radial pulse wave analysis, whole-body impedance cardiography, and plethysmographic finger blood pressures.

Results: Both in supine position and during head-up tilt central and peripheral blood pressure and augmentation index (amplitude of the reflected pressure wave divided by pulse pressure) increased, and time of pulse wave reflection decreased with age. Supine pulse wave velocity progressively increased with age. There were only minor differences in supine and upright systemic vascular resistance, cardiac index, stroke index, and heart rate that were not systematically related to age. In regression analysis, the explanatory factors for a more pronounced decrease in central systolic blood pressure during the head-up tilt were in the age of 50-59 years, higher baseline pulse wave velocity and central systolic BP. None of the changes in other haemodynamic variables during tilt were related to age.

Conclusion: As no systematic age-related differences were observed in cardiac function or vascular resistance, these results support the view that progressive reduction of large arterial compliance contributes to the exaggerated age-related decrease in central systolic blood pressure in response to head-up tilt.