Jamaican health officials are now studying the local implications of new U.S. guidelines redefining "normal" blood pressure as readings below 120/80 mm Hg instead of the usual 140/90.
UP TO May 13, 2003, a blood pressure reading of 140/90 millimetres of mercury (mm Hg) was accepted as normal by the medical community. On May 14, 2003, things changed. On that day the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (a U.S.-based health group) issued their seventh report (the famous JNC reports), redefining and reclassifying normal and abnormal blood pressure.
Their report, published in the May 21, 2003 issue of the Journal of the American Medical Association (JAMA), indicates that based on a review of all the medical evidence, since the last report was published in 1997 (the JNC VI), a blood pressure reading of 140/90 cannot be classified as normal but as stage one hypertension. Normal blood pressure is now defined as any reading below 120/80 mm Hg. Based on the report, a blood pressure reading right at 120/80, previously thought to be good enough, is prehypertension and the patient is prehypertensive if either of the numbers, the systolic (the top number) or the diastolic (the bottom number), is elevated.
This reclassification of normal (and abnormal blood pressure) now places persons with blood pressure readings of 120 to 139 over 80 to 90 in a prehypertensive category with a prescription, not of anti-hypertensive medication, but to adopt a more healthy lifestyle. Untreated hypertension is not to be taken lightly it can lead to cardiovascular diseases including strokes and heart attacks.
Reports are that this new prehypertensive category pulls about 45 million Americans into the hypertension net. Jamaican health officials, who use JNC reports as a guide for local practice, say that they will now have to review data compiled from the 2001 healthy lifestyle survey to figure out how many Jamaicans are now affected.
"The report has made a few new suggestions which are not all that earth shattering, it's just demonstrating something we knew all along but we are just getting the evidence. We have always known from original data that the lower the blood pressure, the better off you are but the evidence to provide the operational intervention was missing," said Professor Rainford Wilks, director, Epidemiology Research Unit, Tropical Metabolism Research Institute (TMRI). "We now all have to look at our data and see how many people are now implicated and who now require health attention."
He said that a definition is based on several criteria statistical, clinical, operational and reiterated that prognostically health officials have known for some time that the lower the blood pressure, the better off their patients are.
Better and cheaper drugs, said Professor Wilks, leading local researcher on hypertension, have also facilitated the shift in definition, since physicians can intervene in cases of hypertension with more limited risks to patients, particularly in terms of drug side effects.
Dr. Deanna Ashley, director of the Health Ministry's Health Promotion and Protection also said that the JNC VII report will have to be reviewed to determine what it means in the local context. She also agreed that the trend in hypertension management is for physicians to try to pick up cases much earlier.
"The earlier we pick up the cases, the easier it is to reduce the risk and complications are less. Depending on how long the patients have hypertension, they may have damaged their blood vessels, and be at possible risk for strokes and other cardiovascular diseases," she said.
Dr. Ashley, spearheading the national healthy lifestyle campaign to squash the spread of chronic diseases here, also pointed out that beside drug therapy, patients have a large role to play in hypertension control. This is the most difficult part of management.
"Patients must make lifestyle changes and it is not just a one-off thing. People have to be convinced to want to do the changes. Writing a prescription and going home will not cut it," she said.
The overall prevalence of hypertension in Jamaica runs 20.8 per cent in women and 19.9 per cent in men but gets to a high of 68.6 per cent and 66 per cent among the 65 to 74 age group in women and men respectively. Dr. Ashley pointed out too, that the focus should extend beyond just hypertension to look at such conditions as obesity, diabetes, strokes, heart diseases because they impact blood pressure and each other.
The JNC VII also recommends the wider use of diuretics (so-called 'water pills') for hypertensive patients with readings above 140/90 and for combination drug treatment for those with more severe blood pressure readings of 160/100 and higher.
JAMA's editorial comment on the JNC VII report indicates that one of the points emphasised by the report is that the focus of hypertension treatment should be placed on systolic (the top number) blood pressure control. The editorial also indicates that cardiovascular risk from systolic hypertension begins at 115 mm Hg and risk from diastolic hypertension begins at 75 mm Hg.
