Cardiovascular reactions to physiological stimuli in the elderly and the relationship with the autonomic nervous system.

In order to evaluate age-related differences in autonomic nervous system control of the cardiovascular system, we studied two groups of healthy subjects of different ages by means of an autonomic function test, the posture test, applied before and after meals. Our results suggest that the reactions of the cardiovascular system to physiological stimuli such as meals or standing up, differ in elderly compared with young people, partly because age modifies the balance between the parasympathetic and the orthosympathetic nervous systems. In the elderly there is a progressive decline in parasympathetic function, which controls the initial heart rate response to standing up. Splanchnic blood pooling and possible hormonal secretions after meals may produce a drop in blood pressure due to cardiovascular modifications in the elderly. Other factors contributing to the different patterns found in the elderly may be reduced compliance of the vascular tree, a decreased baroreceptor response and decreased sympathetic activity.