Re: Why is systolic blood pressure higher in elderly people?

Blood ressure is expressed through three values:
- average pressure is not directly measured, and is issued through 
calculation using systolic and diastolic (see below) values. Nowadays, 
automated devices perform such calculations automatically
- systolic pressure is the value of pressure generated by the cardiac 
contraction. When your heart pushes a certain amount of blood into your 
aorta (heartbeat or systole), the pressure increases up to a maximal 
value (systolic pressure). The heart then relaxes (diastole)and the 
pressure drops to a minimal value (diastolic pressure).

Systolic and diastolic pressures have therefore different meanings. 
Diastolic pressure is the pressure wich remains in your arteria between 
two heartbeats and is the "engine" that propells your blood toward organs 
such as brain, kidneys, liver and so on. On the other hand, systolic 
pressure is a good indicator of the resistance to blood circulation.

In elderly patients, arterial wall becomes infiltrated by fat 
(cholesterol) and becomes less compliant (elastic). While cardiac output 
remains unchanged, resistance to blood circulation increases, and 
systolic pressures becomes higher, diastolic pressure remaining 
unchanged. Hypertension (elevated blood pressure) is a different 
situation, both systolic and diastolic pressure being increased (world 
health organisation states that blood pressure over 160 mm Hg (systolic) 
and over 95 mm Hg (diastolic)is hypertension)

Hope this helps

Luc

Luc Ronchi, MD
Pediatric anesthesia
Hopital de Saint-Nazaire
France