Monday, May 22, 2006

What is hypertension?

At this year's World Hypertension Day, perhaps it is a good time to ask the very simple question, a question that our patient ask us all the time. Doc, What is normal blood pressure?
This question, though very simple, is indeed very difficult to answer. I hear even prominent hypertension specialist have difficulty answering this one, whenever I attend hypertension seminars (which are getting fewer and fewer). Two points are important to note from the offset:

1.The earlier understanding was taken from large scale epidermiological studies like Framingham and Mr FIT where the BP distribution in the community was noted to have a bell distribution and the BP at two standard distribution came out to be 120/80mmHg, anything higher was abnormal.

2. That later clinical trial data, especially from studies in the diabetic population, showed that even at BY of 120/80mmHg, the patient was still at increase risk of CVS events.

Category Systolic (top number) Diastolic (bottom number)
Normal Less than 120 Less than 80
Prehypertension 120–139 80–89
High blood pressure

Stage 1 140–159 90–99
Stage 2 160 or higher 100 or higher

Table taken from National Heart, Blood and Lung Institute, on stages of hypertension.

Because of the above two points, many clinician who work with hypertensive research believes that there is no such thing as normal BP (by number) which fits everybody. The numeric cut-off is only useful for clinical research and clinical trials. For the normal individual, the normal blood pressure is the lowest blood pressure that he can tolerate without dizziness, undue tiredness and lethargy. That number could be 100/70mmHg or less. In fact, the lower the better, as long as there is no dizziness or lethargy. Of course, there must not be any target organ damage. Therefore for the normal individual, the lower the better. Hypotension, in the normal individual should be diagnosed with great caution. This perhaps, is the most important message for World Hypertension Day 2006.

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