The Interaction of Genetic and Environmental Factors in Determining The Resemblance of Arterial Pressure in Close Relatives

Arterial pressure is one of the most variable of human physiological measurements, as can be recognized by an examination of any of the 24 hour records that are produced by the new continuous recorders. There is a general tendency for pressure to increase during the day—mean evening values being a few mm Hg higher than mean morning values. Systolic pressure varies more than diastolic pressure, and in many people the highest systolic pressure during the 24 hours exceeds twice the lowest value ; in some hypertensive subjects systolic pressure by night may be lower than diastolic pressure by day.