People with blood pressure somewhat below the average used to be said to suffer from low blood pressure. The condition was called hypotension. Now records are available of great numbers of people with somewhat lower blood pressures who nevertheless feel quite well, and who seem to be likely to live long.
Hypotension is recognized as a condition in which the systolic pressure is under 80 mm. of mercury or 20 mm. below the usual average of the person concerned. The blood pressure may be quite low after prolonged rest in bed or with malnutrition. The blood pressure may also be lowered by conditions affecting the spinal cord or by the operation which cuts off the sympathetic nervous system.
A feeling of faintness or weakness may be the only indication that the blood pressure is lower than it should be.