Hypertension: A History

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Speaker 1: Welcome to Stuff You Missed in History Class, a production of I Heart Radio. Hello, and welcome to the podcast. I'm Tracy V. Wilson and I'm Holly Fry. I got a physical the other day, always the most fun, so much fun. My blood pressure was high. Not surprising really, because number one, high blood pressure is just incredibly common. It is the most prevalent non communicable chronic disease in the world. But besides that, I'm forty seven and I have hypertension on both sides of my family. So in a lot of ways this has felt inevitable. So naturally, as I have been taking my blood pressure at home, as instructed by my doctor, I have been pondering how humanity figured out that this often symptomless disease even exists. Uh So, today's episode is about how we figured out how to measure blood pressure and how hypertension became viewed as a disease. Most of the detail goes up until the first diuretics were developed, because that marked a big shift in this and after that, so many things happened so fast that it's was it felt impossible to include them all. I did want to note that hypo tension or low blood pressure that also exists. A lot of people experience it as orthostatic hypotension, which is what happens when you stand up too fast and you get that lightheaded feeling. But a lot of people who have hypotension for it's a lot more serious and really life disrupting. But there's not as much historical focus on it because a lot of the time it is connected to something else rather than like a condition that's existing on its own. Um also heads up. Obviously, we're gonna be talking a out blood a lot, and some animal experimentation and some stuff about restrictive dieting, and we don't normally give a heads up about death on the show because death really comes with the territory of a history podcast. It comes up almost every episode. But there's a death in here due to uncontrolled hypertension that I just found a little unsettling to read, So just know that's coming later on. Yeah. So, ancient cultures all over the world used the pulse as a diagnostic tool. This is most documented in ancient Greek medicine and in traditional Chinese medicine and ayur Veda, which are still practiced today. It's also been part of indigenous healing practices in other parts of the world. Many of these traditional systems of medicine incorporate the idea of a person's energy or life force or vitality and keeping that energy balanced. So while a practitioner might be palpating a person's physical pulse, they might be doing so to assess something more metaphysical. The first written reference to something that might have been high blood pressure maybe from the Chinese Yellow Emperor's Classic of Internal Medicine that dates back to about b c E. This text describes the pulse as hardening if there is too much salt in the blood, and treatments for this hardened pulse include acupuncture and the removal of blood through things like blood letting and leeches. There are also references to the pulse being used to diagnose illnesses in several Egyptian medical texts dating back to about thirty five hundred years ago. Some of these directly connect the pulse in other parts of the body to the beating of the heart and to blood flow. Moving ahead to the eleventh century c E. Past podcast subject even Sina, whose name is sometimes westernives does Avicenna wrote quote the pulse is a movement in the heart and arteries, which takes the form of alternate expansion and contraction, whereby the breath becomes subjected to the influence of the air inspired. The first person to document the circulation of blood throughout the body was English physician William Harvey in s so to be clear here, there was already plenty of commentary on various aspects of the heart, the blood, blood vessels, and the pulse. But before this point, the conventional wisdom was at the heart pumped blood out to the tissues, where it left the blood vessels and was absorbed. Harvey, on the other hand, described circulation as a closed loop, with the blood moving through the lungs and out to the body and back. Yeah. I read a paper that described him as single handedly discovering circulation, and I was like, nah, that's a little reductive, building on the work of the people who came before him. The first measurement of the pressure inside this system, specifically in an artery, happened more than a century later, thanks to English clergyman Stephen Hales, who did experiments in all kinds of subjects related to plant and animal physiology. Hales was building off of an invention by past podcast subject Evangelista Torricelli. This was the manometer that was a device used to measure pressure. Torricelli used a mercury filled glass tube, but Hale's approach here was a little bit different. He inserted a brass tube into the artery of a horse, and he connected that tube to a long glass pipe. He wrote about this in his seventeen thirty three treatise Statical Essays containing Hemosthetics. The horse needed to be euthanized because of a fistula on its withers, which at the time was not really a treatable condition, and Hales had it restrained on the ground for an experiment. He wrote quote, having laid open the left curl artery about three inches from her belly, I inserted into it a brass pipe whose bore was one sixth of an inch in diameter. I fixed a glass tube of nearly the same diameter, from which was nine ft in length, then untying the ligature of the artery. The blood rose in the tube eight ft three inches perpendicular above the level of the left ventricle of the heart, but it did not attain to its full height at once. When it was at its full height, it would rise and fall at and after each pulse two three or four inches. So just the note if you go to look for more about this experiment number one, there is a widely used illustration of this experiment that shows the tube and the horse's neck that is incorrect based on what we just read, But beyond that, the experiment continued on from here. It is a little disturbing to read. It resulted in the animal's death, which again the animal needed to be euthanized, but this would not have been the most humane way to do it. For a while after this, most blood pressure measurements were invasive. They involved putting something inside an artery to take a reading. For example, Jean leonar Marie Poise did experiments on dogs and wrote about them in his dissertation recher Left Artique. He placed a mercury monometer into the dog's artery with a barrier of potassium carbonate or potash to keep the blood from clotting. Possoy made a number of observations from this work, including that dog's blood pressure rose and fell as they breathed in and out. Through the mid to late nineteenth century, many doctors and physiologists tried to work out a non invasive way to measure people's blood pressure. Most of them involved measuring how much pressure it took to compress a person's artery until the blood could no longer flow through it, So sort of like if you pinch a straw until you can't suck any liquid through it in anymore. This was a measure of systolic blood pressure, in other words, how much pressure is exerted on the artery every time the heart beats. One such doctor was ju Risson, who wrote a treatise on a device called this phigmometer in eight five. There were several variations on this device, usually combining a mercury column, a pressure gauge or dial, and a piece that would be placed over the radial artery in a person's inner wrist. Sometimes that piece was a flat metal disc or a metal ball, but it was often flexible like a membrane or rubber ball, or a stretched piece of leather like a drumhead. To use this phigmometer, a physician would place the device onto a person's wrist and feel their pulse at a point that was below the device. Then they would press the device. Usually that flexible part into the wrist until they could no longer feel the pulse below it. Then they would look at the gauge or the dial to get a measurement of how much pressure they were exerting. This reminds me a little bit of those tire pressure gauges that have a little thing that shoots out of the end. So this device had some pros and cons. It was not invasive, and compact and portable, but it was also pretty tricky to read, and eventually it became apparent that it wasn't very accurate. It was relying on like a person manually pushing on a thing while feeling something with their fingers. It was just a little prone to error, much like those little tire gauges. In eighteen forty seven, German physiologist Carl Ludwig developed a chemography on which combined amnometer with a stylus and a revolving drum to record variations in blood pressure on a graph. Unlike Harrison's figmometer, this was invasive. The mnometer had to be placed in an artery, and Ludwig used this for experiments on dogs, but it did make it possible to record ongoing fluctuations in blood pressure. As they were happening in the eighteen fifties and sixties, lots of physicians and physiologists were still trying to find non invasive ways to measure blood pressure, now, ones that would be more consistent and more precise than this pigmometer was. One result was this figma graph that was developed and improved by multiple people, including German physiologist Carl von der Roort and French physiologist Etien joul Maray. This was a device placed over the inner wrist. It used springs and levers to magnify the movement of the radial pulse and then all this was connected to a stylist that could record that movement as a graph. If small weights were placed onto the device slowly weighing it down, the pulse would eventually stop, so this could also provide a measurement for blood pressure. Starting in the eighteen seventies and continuing until his death in eighteen eighty four, Frederick Akbar Mohammed researched blood pressure at Guy's Hospital in London. Mohammed was born in England and was of Irish and in the descent, and he developed and improved quantitative spygmagraph While he was still in medical school, and he used this to make a lot of significant discoveries about blood pressure and circulation over the course of about a decade. Some of the patients he worked with were under the care of his colleague Richard Bright. Mohammed was able to determine that patients who had kidney disease then known as Bright's disease tended to have higher blood pressure. He also found that there were people who had higher blood pressure but no evidence of kidney dysfunction. He crossed reference to his blood pressure measurements with autopsy reports to document how high blood pressure could be related to things like kidney damage, arterial fibrosis, and youeurysms and enlarged hearts. Sometimes he was credited with coining the term essential hypertension, although sometimes that credit goes to physiologist Otto Frank, who was working a few decades later. Mohammed was one of the first people to suggest that lowering a per since blood pressure could prolong their life, and that is something we will get too more after a sponsor break Frederick Akbar. Mohammed's contributions to the study of blood pressure and hypertension are notable on their own. I mean he made a lot of connections that still hold up today. They're even more impressive considering that he was using equipment that could be fiddly, encumbersome. Set up tended to be complicated, it wasn't particularly comfortable for the patient. Using a spig McGraph often involved strapping the patient's forearm to a chair in a particular position, and then if anything was misaligned and those levers and springs, the readings would be inaccurate. But in the eighteen eighties people started developing tools to measure blood pressure that are a lot more in line with what is used today. The first was Siegfried Karl Ridder von Bosch, who was a Jewish physician from Austria. In eighteen eighty one, he developed an inflatable bag that could be pressed against an artery. It was connected to a pressure gauge, so a physician could record how much pressure it took to collapse an artery until blood could no longer pass through. Italian physician Shipione Riva Rocchi improved on this in eight he created an inflatable cuff that could be placed around the patient's arm and then the physician would once again feel the person's pulse below the cuff. As the cuff was being inflated, when the pulse stopped, they would measure that number on a pressure gauge. This was essentially this Figmomme monitor that is still used to measure blood pressure today. A key difference, though, was that Riva Rocchi's cuff was pretty narrow, so as it inflated, it would make a pretty sharp crease in people's flesh, and that could reduce the accuracy of the readings. In nineteen o one, German physician hinrichs On Recklinghausen improved on Riva Rocchi's design by making the cuff eier. Soon this device was being introduced into other parts of the world. Theodore Janeway and Harvey Cushing helped popularize it in the United States. Until this point, most non invasive blood pressure measurements that involved feeling a person's pulse or less frequently using some kind of device to create a graph. And n OH five Nikolai Kortakoff used ascultation, or listening, paying attention to the sounds of the turbulence in a person's artery while inflating and deflating the cuff. He noticed a distinct set of sounds depending on how much pressure the device was exerting on a person's arm relative to their blood pressure. He was using a stethoscope to do this. Obviously, with the cuff on but not inflated, there was no sound. If the cuff was inflated to a greater amount of pressure than the person's systolic blood pressure, there would still be no sound because no blood could get through. But as he reduced the press sure again he started to hear sounds as small amounts of blood were able to get through the artery with each heartbeat. That onset of sounds marked the person's systolic blood pressure. These sounds went through a series of changes as he further reduced the pressure in the cuff, and then the sounds would disappear entirely. And the point where the sounds disappeared was the person's diastolic blood pressure. It's the blood pressure in between heartbeats. I don't think we've said before. These sounds are still known as corticough sounds today. They are still used when somebody is measuring blood pressure using us big momentometer and a stethoscope. There are some variations that exactly when in the cycle people think is the best time to say that's the diastolic blood pressure. Though, as has been the case with so so many other medical innovations on the show, even though this provided a practical, reliable, noninvasive way to measure most systolic and diastolic blood pressure, the medical commune it he did not adopt it right away. Some doctors just didn't like the idea of using a device like this in medical practice. In the words of an article in the British Medical Journal, by using machines as part of medical diagnosis, quote, we popularize our sense and weaken clinical acuity. Others just thought that a doctor's fingers were a better, more sensitive tool than a stethoscope. There were also people who had been using things like spigma graphs or other devices, and they felt like the spigmommometer was making things too easy. Like I said earlier, spigmo graphs could require a lot of technical skill and precision to set them up and use them correctly, and so there was this sense that by being simpler and easier to use, the sphigmo mimometer would just make the practice of medicine less prestigious. The sphigmommometer made it much easier to measure more people's blood pressure, though, so over the first three decades of the twentieth century, researchers started seeing lots of connections between high blood pressure and heart diseases, strokes, and death. This was all happening in spite of the controversy over this figmomnometer that was playing out in the medical community, because most of this research was happening actually in another industry entirely, and that was the life insurance industry. Life insurance companies wanted to make sure that as often as possible the people they were covering had a long life and paid lots and lots of premiums before their policies had to be paid out. So by the end of the nineteenth century, assessing a customer's health had become an established industry practice. If somebody wanted insurance, they would be examined by an insurance company physician, and then underwriters would use the physician's report to decide whether ensuring this person was an acceptable risk for the company. Over time, all this data would inform things like actuarial tables that the company could use to estimate how long a person could be expected to live. Here in the US, it's pretty much still how it happens today, although there are plans that don't require physical exams, and a lot of plans that are offered through employers as an employee benefit don't require an exam below a certain monetary threshold. In nineteen o six, Northwestern Mutual Life Insurance Company started measuring the blood pressure of all of its clients as part of their insurance applications. Other insurance companies followed suit. In nineteen eleven, Dr J. W. Fisher, medical director of the Northwestern Mutual Life Insurance Company, gave an address before the Medical Directors Association which set, in part quote, no practitioner of medicine should be without a spigmomanometer. He has in this instrument a most valuable aid in diagnosis. This figmomanometer is indispensable in life insurance examinations, and the time is not far distant when all progressive life insurance companies will require its use in all examine nations of applicants for life insurance. By the nineteen thirties, the life insurance industry had gathered data from more than ten million people. They're putting together reports on that data, and it showed clear connections between high blood pressure and other diseases, including cardiovascular diseases and kidney disease. There was also a clear correlation between high blood pressure and a shorter life expectancy. This data still had some big limitations though. Number One, These companies were primarily ensuring white people, specifically white men, as we talked about in our episode on Maggie Lena Walker. There were mutual aid organizations, fraternal orders, and other organizations that offered insurance to people of color, but they were not included in this data set. Number two. As the company saw correlations between hypertension and early death, they started declining coverage for people whose blood pressure was too high. Number three. There was a lot of ongoing follow up. People were either approved for insurance or they weren't, and unless people wanted to change their coverage and that change required another examination, the company did not check in on them again until they died. Although the life insurance industry had a wealth of data suggesting a connection between high blood pressure and other diseases and reduced life expectancy, there was still a lot of debate about all this in the medical community. Measuring patients blood pressure eventually did become a standard practice and by the nineteen teams, at least some doctors and researchers thought high blood pressure should be classified as a disease, but there was a lot of disagreement about how to define. High blood pressure is generally measured in millimeters of mercury, and the idea that one twenty over eighty millimeters of mercury was normal that showed up pretty early in this whole process. But some experts in the early twentieth century thought that normal got higher as people age, and various researchers cited numbers as high as one eight over one ten as normal. There also was not a consensus about what caused high blood pressure, or whether high blood pressure was really the body's compensation for something else, so a lot of doctors thought lowering a person's blood pressure might do them more harm than good, because what if their blood pressure needed to be that high to move their circulation through clogged or hardened arteries, for example. To add to all of that, there weren't really effective treatments for hypertension at this point, even if a doctor wanted to try. The idea that salt intake, or more specifically sodium might cause high blood pressure that had been around since nineteen o four, when l Umbard and E. Bojard published Cause de lie potension on arterial so based on that, doctors often advised patients whose blood pressure was high to reduce the salt in their diets. But there had been pay Shans and that first study by Ambard and Bojard whose blood pressure did not increase with their salt consumption. These low salt diviots could also be really hard to stick to. Plus there was i mean evidence going back from this very first study that they might not work for everybody. Doctors also tried various drugs to lower blood pressure in the early twentieth century and found them to be only somewhat effective at best. On a lot of these drugs had serious and sometimes dangerous side effects. So with all of that in mind, a lot of doctors thought that as long as a patient wasn't showing other symptoms, their blood pressure should be left alone. In British cartiologist John H. Hay wrote an article in the British Medical Journal that's said, in part quote, there is some truth in the saying that the greatest danger to a man with high blood pressure lies in its discovery, Because then some fool is certain to try and reduce it. Sometimes that first part of the quote is left out, making it seem like the saying he was quoting was actually his entire statement, and that he thought it was foolish to try to reduce blood pressure. But this was in the context of an article that started quote, no one can now afford to be indifferent to the problems associated with variations in blood pressure. For a high pressure is an abnormality which always demands investigation, supervision, and careful treatment. American cardiologist Paul Dudley White echoed Hayes sentiments a few years later in nine seven, quote, the treatment of hypertension itself is a difficult and almost hopeless task in the present state of our knowledge, and in fact for aught. We know the hypertension maybe an important compensatory mechanism which should not be tampered with, even if it were certain we could control it. A few years after that, though, President Franklin Delano roosevelt death brought renewed focus to all of this. We'll talk more about that after a sponsor break. The death of President Franklin Delano Roosevelt brought some more public awareness to the risks of uncontrolled hypertension. Roosevelt was first diagnosed with hypertension in ninety seven, when he was fifty four. At that time, his blood pressure was measured at one sixty two over. No treatment was prescribed for him until four years later, when his BP was measured at one over one oh five. As we said earlier, though at this point treatments for hypertension were really limited, so the President was put on a low fat, low sodium diet. He was advised to rest and get massages, and he was put on the barbiturates phena barbital, which today is most often used to treat seizure disorders as well as anxiety and sleeplessness. This course of treatment was not effective, and in February of nine, Roosevelt's blood pressure was measured at two sixty over one fifty. He was also starting to show signs of heart and liver failure. He attended the Yalta Conference, which was a meeting of Allied leaders to discuss the post World War two reconstruction, and other people present expressed concerns about his health, including doubts about whether he was cognitively alert. During that meeting, Winston Churchill's physician remarked that Roosevelt looked like a man who only had a few months to live. His blood pressure was not the only thing involved in his overall health, but that is the focus of this episode, so that sort of sticking to On April twelfth, Roosevelt reported a bad headache while he was sitting for a portrait. His blood pressure was recorded at that time at three hundred over one. Not long after that, he lost consciousness and died at the age of sixty three. No autopsy was performed, but his cause of death was reported as a cerebral hemorrhage. It's a logical conclusion to draw from the symptoms that were shown at the time. His physician, Admiral Rossty McIntyre, reportedly said that this quote came out of clear sky. Even though the president's blood pressure had been escalating for years and was three day there was still a lack of medical consensus about what to do about high blood pressure. Though Tyson's Practice of Medicine is a major medical textbook and in its edition had this to say about hypertension. Quote, may not the elevation of systemic blood pressure be a natural response to guarantee a normal circulation, To the heart, brain, and kidneys. Essential hypertension. Over zealous attempts to lower the pressure may do no good and often do harm. Many cases of essential hypertension not only do not need any treatment, but are much better off without it, so it was pretty clear at this point that more medical research was needed. There was a rice based diet developed by Walter Kempner that was sometimes effective at reducing a person's blood pressure, but it was extremely restrictive and not usually sustainable over the long term. Various drugs are being used to try to treat hypertension, but at this point they all had some pretty unpleasant or even dangerous side effects. Ralphina serpentina or Indian snake root, was developed into an anti hypertension drug Resurping in India, and while it could lower a person's blood pressure, it didn't work for everyone, and it was also associated with things like vomiting, nightmares, and chest pains. Hadrolyzine was a vasodilator that could cause headaches and rapid heartbeat, and at large doses could cause a syndrome that resembled lupus. Hexamathynium was a ganglion blocking agent that had to be administered as injections, sometimes multiple times a day. There were also attempts to control people's blood pressure through surgeries. One was sympathectomy, or severing sympathetic nerves near the spine. Another involved the removal of the adrenal glands. While a person's blood pressure might be lower after one of these procedures, this definitely was not true for everyone, and these procedures were also really risky and irreversible. There are a lot of things that were just regarded as quackery also, and we are not getting into any of that. In President Harry Truman signed the National Heart Act into law. This law noted that diseases of the heart and circulatory system had become the leading cause of death in the United States. This law established the National Heart Institute and the Public Health Service, as well as the National Advisory Heart Council. The Framingham Heart Study was launched soon afterwards with the goal of determining the causes of heart disease. The Framingham Heart Study is actually still ongoing today. They're on their third generation of research participants. Through the Framingham Heart Study and other large scale long term study ease it became increasingly clear that hypertension could cause heart and kidney problems, including issues like left ventricular hypertrophy, and that lowering a person's blood pressure could help prevent and sometimes even reverse these issues. But actually reducing people's blood pressure continued to be really difficult, so many doctors continued to treat hypertension only if it seemed to be causing some other issue. When hypertension wasn't being caused by some other disease or disorder, it was increasingly known as essential hypertension, and many doctors saw it as just an inevitable part of aging. That started to change in the fall of nineteen fifty seven when a clinical trial started for a diuretic called chlorothiazide. This wasn't intentionally intended to be used as a treatment for hypertension. Was the diuretic that doctors were prescribing to patients who had edema due to congestive heart failure. But when doctors gave their patients this medicine, they noticed that their blood pressure dropped dramatically in night. This became available at pharmacies under the brand name di a Ill. This was during the massive boom in pharmaceutical development that took place during and after World War two. So many new drugs and classes of drugs were developed during this period, several of which have come up on the show before. Antibiotics entered mass production during the war and flourished afterward. The first oral contraceptive was approved in nineteen sixty after having been used to treat various gynecological disorders for a few years before that. Tranquilizers were also introduced during this era, which we talked about in our two parter on the litamide. So Diarill was introduced at a time when there was just an increasing focus on the idea that chronic illnesses and conditions could be treated or controlled using pharmaceuticals. It played a really big part in that shift. At this point in the United States, the pharmaceutical industry not advertise drugs directly to consumers, but merk Sharp and Dome, which was the company that developed Direll, did things like distributing research reports to science writers, which led to favorable write ups in publications like Readers. Digest Mark also advertised to doctors in medical journals, and they created a character called di a rill Man as part of this campaign. This was a transparent illustration of a man with the heart and lungs and urinary system visible in that illustration. Di arell Man became one of the first examples of a physical gift that drug sales reps would leave with doctors. This is a little transparent desk figuring about six inches tall that had these organs visible on the inside of it, and it was mostly filled up with water. I want one so bad now you might be able to find one on eBay. Oh, I'm gonna go looking. Although di arell could still cause side effects like lightheadedness and digestive problems, it was overall more broadly effective than the earlier drugs that were used to treat hypertension, and those side effects were generally less serious and more widely tolerated. This made it possible to get a lot more data about what worked and what happened when a person's high blood pressure was lowered. As direl was making its way to market, Dr Irvine Page proposed the mosaic theory of hypertension. This built on ideas he had started putting forth as early as ninety seven, and he argued that there were multiple interrelated factors at work in maintaining the bodies blood pressure equilibrium. You thought that blood pressure involved genetic, environmental, anatomical, adaptive, neural, indocrine, humoral, and hemodynamic factors. You can get a direl man for just like twenty five bucks. Di arell marked a major shift in the treatment of hypertension, and thanks to that shift, it's tricky to do a historical playbi a of all the new developments since then, even just as highlights, because simultaneously, so much has happened in terms of drug development and research into hypertension, and so much is still unknown. Like diarrhal and other, diuretics were just the first class of drugs developed to treat hypertension. Today there are at least ten, including beta blockers, ACE inhibitors, and calcium channel blockers, most of which were introduced over a period of only about thirty years. The availability of these drugs and others made it possible to conduct things like randomized, placebo controlled, double blind trials of hypertension treatments. The first of these were conducted through the US Veterans Administration. These studies have provided clear evidence that reducing moderate and severe hypertension is beneficial and can prolong people's lives. Based on this and other data, widespread public education campaign started in the nineteen seventies for both doctors and the general public. This includes the National High blood Pressure Education Program, which launched in the US in nineteen seventy two. There have also been so many other studies since then, including other studies at the v A. They've looked at so many questions around things like correlations with other conditions, race, gender, the efficacy of different drugs, diet, exercise, age, tobacco used, diabetes, on and on and on. Through this research, guidelines for how to define high blood pressure and how to treat it have become increasingly aggressive and specific. For example, in the US, the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High blood Pressure issued its first report in nineteen seventy seven. This report suggested that a person who's blood pressure was one sixty over ninety five should have it checked again in a month, while people fifty and under should be checked every two to three months. If their blood pressure was between one forty ninety and one six probably not how a doctor would approach it today. It's definitely not how my doctor did. And this report, treatment was recommended only if a person's dia stylic blood pressure was greater than or equal to one oh five. Those numbers have dropped repeatedly since the seventies. Most recently in seventeen, the American Heart Association and the American College of Cardiology announced new guidelines that defined normal blood pressure has less than one twenty over eighty, and everything above one thirty over eighty is classified as some variety of hypertension. A systylic reading above one eighty and a dia stylic reading above one twenty either of those that's classified as a hypertensive crisis, and the American Heart Association advises people to contact their doctor immediately if this happens to them. This is so radically different from earlier eras when there were studies that classified one eight over one ten as normal. There is also various conventional wisdom around hypertension that still isn't fully supported or understood. We noted earlier that a possible connection to sodium was first proposed in nineteen o four. Today you can read all kinds of extremely authoritative, yet totally contradictory, peer reviewed papers that describe sodium as everything from the single biggest contributor to hypertension in the entire world to something that can contribute to hypertension in some people, but only if they are sensitive to sodium yets. I found this very frustrating as I was trying to get to this part of the episode. Another bit of conventional wisdom has involved associating high blood pressure with being overweight, and with recommendations for people to lose weight included as a way to try to control their blood pressure. But that is seemingly not as straightforward as all that number one and abody can have high blood pressure regardless of how much they weigh and number two. For a long time, there was really only one size of blood pressure cuff that was being used, and it was really too small for people with bigger arms. It gave artificially high readings for people who weighed more. Blessed people tends to weigh more as they get older, and some of the very earliest actuarial reports about this noted that quote the increase of blood pressure with increasing percentage of overweight is exaggerated because of that interaction between people's age and their weight. Today, researchers are looking at people's genetics, salt sensitivity, congenital factors like birth weight and stress during fetal development and so many other factors. But the reality at this point is that for the overwhelming number of people who have hypertension, we don't know exactly why. We really don't know. It's also frustrating. Also, while the blood pressure cuff has been a stay entered piece of equipment for doctors and nurses and various other health and medical practitioners for more than a century, there are improvements in the works for that as well. So beyond just cuffs that inflate themselves and then give a readout of blood pressure and pulse on a screen like I've been using at home as my doctor instructed, there are also efforts to make noninvasive blood pressure measurement tools that don't actually require a cuff at all. They would work a little more like a pulse oxometer that goes on a person's fingertip. That technology also needs some work. Uh. We know at this point that pulse oxometers often don't give readings that are correct on people with darker skin, So there's there's a whole confluence of things to keep in mind. There there are some finger monitors that have already hit the market at various points, but they've generally been seen as less accurate than monitors that use a cuff, and then rist monitors that are also on the market today are similarly seen as less accurate than ones go around the upper arm. Um. There would be a lot of pluses to having an accurate way to measure blood pressure that didn't require a cuff, in part because try and put a cuff on yourself is annoying. So that's um. That's the brief history of hypertension, especially up through the introduction of di rill. Uh. This is not a solicitation for advice about my blood pressure. Please and thank you. Tracy has a doctor. I sure my doctors on the ball with my blood pressure. Do you also have listener mail I do? This is from Samantha. This is one of many, many, many notes that we got about this. It was something that had crossed my radar first thing in the morning. Um, and I'm sure I will say it again on a future installment of on Earth, but this the next Unearthed, is all the way in October, and I would rather say something about it now. So Samantha wrote, hello there. I came across this article today and remembered that you both had done an episode to part if I remember correctly on Jim Thorpe. You probably already saw it, but I thought i'd pass it along just in case. I'm always behind on the podcast, so my apologies if it's already been mentioned. Can't wait to hear more. And Samantha sent an article about Jim Thorpe's Olympic record being restored. Jim Thorpe is the subject of the only three parter we have ever done on the show so far, and one of the things that we talked about was a whole controversy involving whether some of his athletic participation disqualified him from being an amateur athlete. And so just on I think what was gonna be the one anniversary of one of his Olympic wins, um his Olympic record was restored. So uh, I'm sure I will have a more thorough discussion of that at the next un Earth, which is not until October, so it was too good of a thing to wait until them. If you would like to send us a note about this or any other podcast, where a history podcast that I heart radio dot com and we're all over social media at miss in History. You'll find us there for your Facebook, Twitter, Pinterest, and Instagram, and you can subscribe to our show on the I heart Radio app and wherever else you like to get podcasts. Stuff you Missed in History Class is a production of I heart Radio. For more podcasts from I heart Radio, visit the i heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.