Why have previously “normal” or “highnormal” levels of blood pressure been reclassified in the JNC 7 guidelines?
In previous guidelines, levels of blood pressure between 120 to 129 mm Hg systolic and/or 80 to 84 mm Hg diastolic were classified as “normal,” and those between 130 to 139 mm Hg systolic and/or 85 to 89 mm Hg diastolic were classified as “high-normal” or borderline. The incorporation of both “normal” and “high-normal” into “prehypertension” is predicated on 3 facts: (i) Blood pressures tend to track over time, so that those who have higher than optimal levels, ie, above 120/80 mm Hg, are more likely to progress toward established hypertension defined as a blood pressure of 140/90 mm Hg or higher.3 (ii) Those with blood pressures in the previous “normal” and “high-normal” groups in the Framingham Heart Study cohort who were followed for an average of 12 years experienced a significantly higher rate of overt cardiovascular events than did those with blood pressure of less than 120/80 mm Hg.4 (iii) Beyond these limited data, there are observational studies on over 1 million people that h
