blood pressure

In the United States, blood pressure is usually measured in millimeters of mercury (mmHg). Two measurements are made. The first number is the pressure as the heart pumps (systolic pressure). The second number is the pressure between beats (diastolic pressure). The two can be thought of as the maximum and minimum pressure.

High blood pressure (hypertension) is associated with various diseases, such as stroke and heart attacks. In 2003, a committee convened by the National Heart, Blood and Lung Institute issued the following guidelines:¹

Average diastolic blood pressure	Average systolic blood pressure
Average diastolic blood pressure	less than 120	120–139	140–159	160 and higher
less than 80	normal	prehypertension	hypertension, stage 1	hypertension, stage 2
80–89	prehypertension	prehypertension	hypertension, stage 1	hypertension, stage 2
90–99	hypertension stage 1	hypertension, stage 1	hypertension, stage 1	hypertension, stage 2
100 and higher	hypertension, stage 2	hypertension, stage 2	hypertension, stage 2	hypertension, stage 2

Older Stagings

Formerly the stages of hypertension were described as mild, moderate, and severe. Unfortunately, describing a condition as “mild” encourages people to do nothing about it. In 1992, the National High Blood Pressure Education Program released the staging shown in the table below. The numbers 1 to 4 represent increasingly greater risk.

Average diastolic	Average systolic blood pressure
Average diastolic	<120	120–129	130–139	140–159	160–179	180–209	>209
<80	optimal	normal	high normal	1	2	3	4
80–84	normal	normal	high normal	1	2	3	4
85–89	high normal	high normal	high normal	1	2	3	4
90–99	1	1	1	1	2	3	4
100–109	2	2	2	2	2	3	4
110–119	3	3	3	3	3	3	4
>120	4	4	4	4	4	4	4

Physicians came to believe that people in the "high normal" group actually have a significantly increased risk of heart disease. Some results² of the Framingham Heart Study, which has followed thousands of persons over half a century, suggest, for example, that women in the "high normal" group were twice as likely to have a "cardiovascular event" as women whose blood pressure was below 130 mmHg systolic and 85mmHg diastolic.

1. Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Traetment of High Blood Pressure.
Journal of the American Medical Association (JAMA), May 21, 2003.

2. Ramachandran S. Vasan, Martin G. Larson, Eric P. Leip, Jane C. Evans, Christopher J. O'Donnell, William B. Kannel, and Daniel Levy.
Impact of High-Normal Blood Pressure on the Risk of Cardiovascular Disease.
New England Journal of Medicine, volume 345, number 18, pages 1291-1297. 1 November 2001.