Definition and Classification of Hypertension

Definition
There is a continuous relationship between the level of blood pressure and the risk of complications. Starting at 115/75 mmHg, CVD risk doubles with each increment of 20/10 mmHg throughout the blood 1,2 pressure range. All definitions of hypertension issued by various international authorities are arbitrary. While it is possible that the risk of cardiovascular events in Asian Indians is higher at relatively lower levels of blood pressure (BP), in the absence of any such data from India, it would be prudent to avoid any further confusion and maintain the same definition proposed in the first Indian 3 guidelines on management of hypertension (2001).

Hypertension in adults age 18 years and older is defined as systolic blood pressure (SBP) of 140 mm Hg or greater and/or diastolic blood pressure (DBP) of 90 mm Hg or greater or any level 2,3 of blood pressure in patients taking antihypertensive medication.

Classification
The positive relationship between SBP and DBP and cardiovascular risk has long been recognized. This relationship is strong, continuous, graded, consistent, independent, predictive, and etiologically 4,5 significant for those with and without coronary heart disease. For persons over age 50, SBP is more 6 7,8 important than DBP as a CVD risk factor. SBP is more difficult to control than DBP. SBP needs to be as aggressively controlled as DBP. Therefore, although classification of adult blood pressure is somewhat arbitrary, it is useful to clinicians who make treatment decisions based on a constellation of factors including the actual level of blood pressure. Table 1 provides a classification of blood pressure 3,9 for adults (age 18 and older). This classification is for individuals who are not taking antihypertensive medication and who have no acute illness and is based on the average of two or more blood pressure readings taken at least on two subsequent occasions, one to three weeks apart, after the initial screening. When SBP and DBP fall into different categories, the higher category should be selected to classify the individual's blood pressure.

2 It is felt that the more recently coined term “prehypertension” includes a wide range from normal to high normal. The high normal group needs to be treated in presence of family history of hypertension 10 and concomitant diseases like diabetes and target organ damage (TOD). Also, the term prehypertension introduced in the JNC VII guidelines is more likely to create anxiety in a large subset 9 of population. Hence, we do not recommend the use of the term “pre-hypertension.”