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For most of human history, blood pressure was unknown. It was first measured in 1733 by Stephen Hales, an English pastor who lived in a simpler time when religion and science were not seen as mutually exclusive. His 1733 鈥�贬忙尘辞蝉迟补迟颈肠办蝉鈥� describes how he 鈥渃aused a mare to be tied down alive on her back鈥and] having laid open the left crural artery鈥nserted into it a brass pipe...鈥� The famous artist鈥檚 drawing of the historical event mistakenly has the tube inserted into the horse鈥檚 neck. When he unclamped the artery, he saw the blood rise up the tube and oscillate up and down 2 or 3 inches with each heartbeat. Thus was blood pressure measured for the first time.
However, for blood pressure to have any clinical value there needed to be an easier to way measure it, since human patients tend not to be as accommodating as horses. It was Siegfreid Karl Ritter von Basch that made the next great advance in 1881 by creating a machine that did not require one to puncture the artery. His device used an inflatable bag that would compress the artery from the outside and measure the pressure when the blood flow was halted. Then, Scipione Riva-Rocci in 1896 improved upon the design by creating the wrap-around arm cuff that most people are familiar with today. Finally, in 1905 Nikolai Korotkoff documented how by listening to the artery being compressed one could determine both the systolic and diastolic blood pressure of the patient. His combination of the stethoscope and sphygmomanometer (cutting edge technology at the time and largely unchanged over the past century) became the gold standard of blood pressure measurement.
However, not everyone was enthusiastic about the development of the new blood pressure machines. In 1905, the British Medical Journal complained that with the growing reliance of technological machines for medical diagnosis 鈥�.鈥� To be fair, this complaint has been repeated many times over the past century with virtually every new technological innovation.
However, with the first major hurdle overcome, the debate was no longer about whether we could measure blood pressure but whether we should measure blood pressure. Interesting, it was not medical science that provided the first impetus to measure blood pressure but the insurance industry. In 1906, the North Western Mutual Life Insurance Company began measuring blood pressure in their customers. Their analysis led them to conclude that high blood pressure led to an early death (an insight the insurance industry would repeat with smoking). Its use spread quickly amongst insurance examiners and then to the medical community at large. By 1914, in the , J. W. Fisher declared, 鈥渘o practitioner of medicine should be without a sphygmomanometer.鈥�
Bolstered by this insight from life insurance data, the measurement of blood pressure became a routine practice. But now that blood pressure was, for the most part, accepted as something worth measuring, the next controversy became whether we should be taking steps to lowering. Many people at the time spoke of essential hypertension. The idea was that high blood pressure was a compensatory mechanism of the body. Essentially they theorized that high blood pressure helped push blood through clogged arteries and was a desirable feature. Many of the most prominent physicians of the day initially argued against lowering blood pressure.
鈥淕et it out of your heads, if possible, that high pressure is... the feature to treat.鈥�
- William Osler, to Glasgow Southern Medical Society
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鈥淗ypertension may be an important compensatory mechanism which should not be tampered with, even were it certain that we could control it.鈥�
- , cardiologist
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鈥淭he greatest danger to a man with high blood pressure lies in its discovery, because then some fool is certain to try and reduce it.鈥�
听听听听听听听听听听听 - , British Medical Journal 1931
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Despite this opposition, key studies soon demonstrated that hypertension was neither necessary nor beneficial. In 1948, researchers began the Framingham Heart Study, a massive undertaking where residents from the town of Framingham Massachusetts were enrolled a life-long project to study heart disease. The study is still going on 70 years later with the original subjects鈥� children and grandchildren taking part. Framingham provided some key insights into the causes of heart disease, namely smoking, diabetes, cholesterol and of course blood pressure. It also coined the term 鈥渞isk factor.鈥� But most importantly it showed that blood pressure caused heart disease, not the other way around. In 1967, the Veterans Administration Cooperative Studies also showed that lowering blood pressure prevented strokes. This was the first of many studies to show a clear benefit to blood pressure treatment.
So having resolved the issue of whether we should in fact lower someone鈥檚 blood pressure, we come to the current controversy of how much that blood pressure should be lowered.
It is worth noting that our idea of an 鈥渁cceptable鈥� blood pressure has been steadily falling over the past 50 years. The best example of how permissive we used to be is who over the course of his presidency had blood pressures of over 160 that steadily climbed to over 200 mmHg before his death. His physicians never prescribed any treatment apart from barbiturates and massage. That he died of a stroke while in office is unsurprising in retrospect.
For a long time blood pressures of 180mmHg were not considered significant. Even as late as 1980, the Oslo study labeled people with blood pressures between 150 and 180 as having 鈥渕ild鈥� hypertension. Today numbers such as these are enough to send some physicians into an apoplectic panic.
Over time, the target for blood pressure treatment was lowered to 140mmHg because of a number of trials like the . More recently, studies like and the demonstrated a benefit to lowering blood pressure below 140, which is what prompted the guideline change. But not all studies have shown a benefit. The is a recent example where going below 140mmHg did not translate into a cardiovascular benefit.
Lowering blood pressure too much can be dangerous and lead to dizziness, fatigue or fainting episodes. There is clearly a 鈥溾�� where you lower the risk of cardiovascular disease without causing symptoms. Where that sweet spot is remains a subject of debate, though it seems pretty clear from the evidence that it is somewhere between 120-140, and likely hovers around 130mmHg.
Therefore the current hypertension guidelines controversy is in many ways much ado about nothing. Given the history of controversies we have endured with respect to blood pressure it is remarkably minor. First we had to figure out how to measure, then whether we should measure it all, then whether we should bother trying to lower it, and now how low we should go. And given that we used to tolerate blood pressures of up to 200mmHg, the current argument of 130 vs. 140 is a very minor disagreement indeed. The average reader would best be served by ignoring the current disagreement. Worry about it too much and it will inevitably raise your blood pressure.
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