Standards for assessment of high blood pressure, without regard to age, have been established by the World Health Organization (WHO), as shown in this chart.

Individual blood pressures vary greatly both on a daily and a seasonal basis. These variations are even more pronounced in the hypertensive patient. Normally the blood pressure rises while at work and is at its lowest during the sleeping period.

Shown is data for measurements taken every 5 minutes. the click line represents sleep. the rises is blood pressure at 4PM ( A in the graph) and 12 PM ( B in graph) correspond to an attack of pain and sexual intercourse. ( Beven, Honour & Scott. Sci 36:329,1969)