Because they say so
Before the discoveries of Copernicus and Galileo, the Sun orbited the Earth. It didn't, of course, but everyone accepted that it did because the popes and the Roman Catholic Church told them so.
Medicine operates in a similar fashion. Its governing bodies determine the measure and tempo of disease, which we all go along with, and the pharmaceutical industry pockets the profits.
One good example of medicinal decree is the definition of high blood pressure, or hypertension, the subject of our main story this month. This autumn, America's National Institutes of Health will meet to discuss whether the determinants for hypertension need to be changed once again. Right now, a 'healthy' blood pressure reading is 120/80 mmHg. In 2003, a normal reading was 128/80 mmHg and, before that, common sense prevailed.
Much pivots on the decision. The pharmaceutical industry is pushing for an even more conservative definition because profits improve when a new band of people is suddenly classified as 'ill' and so in need of their products. But there's a minority band of researchers who are calling for the re-introduction of common sense. They are suggesting that medicine has had blood pressure seriously wrong for all these years. They argue that only the systolic level matters in the over-50s, the major target group for antihypertensive drugs.
Others argue that it's almost impossible to get an accurate blood pressure reading as levels fluctuate wildly during the day, and even from arm to arm. Many also suffer from 'white-coat hypertension'-their blood pressure races up just from being in the doctor's surgery. In short, blood pressure levels are not a constant, so hypertension is not necessarily a disease in the sense in which we understand the term.
What is very clear is that many millions of people are taking a powerful antihypertensive drug-such as an ACE inhibitor-unnecessarily. Around 45 million Americans were suddenly caught up in the hypertension net when the readings were changed in 2003, and many millions more are taking the drugs needlessly if the systolic theory is correct. A new report suggests that up to 40 per cent of people diagnosed with hypertension don't have the problem at all, but are merely victims of 'whitecoat hypertension'.
This is potentially bad news for the drugs industry, which is currently selling around $26 billion of antihypertensives every year. Of course, nothing is likely to change. The Sun will continue to go around the Earth, and millions of 'patients' with high blood pressure will still have the problem after the National Institutes of Health meets.