I woke up the other day to the major newspapers breaking the results of a new study that showed more intensive blood pressure treatment to less than 120 systolic reduced the rate of heart attacks by 30 per cent and mortality by 25 per cent. I was a little peeved that I had to read the information in the paper, before the entire study was published and secondly because of the barrage of phone calls that the articles would generate.
If you are planning to call your doctor, let me save you a call. The detailed study results will only be released in a few months. So no new recommendations will be made till we dissect the study and the price the patients paid with regard to side effects to achieve this new goal. While we are talking about medical information in the papers, I will let you in on a little secret in the medical data world. The risk reduction that you read about is what we call relative risk reduction. Confused? Let me elaborate. Say a group receiving a treatment has a rate of heart attacks of 16 per cent, and the group that did not receive the treatment has a rate of heart attacks of 20 per cent. You would assume that the risk reduction is 4 per cent. That is the absolute risk and not what is reported. The relative risk in this case is 20 per cent and that is what is reported in the media. The relative risk in a rough calculation is 16/20, which is 0.8, the remaining .20 translates into the relative risk reduction. Still confused? Welcome to the club.
Now I may have got a little ahead of myself. You may ask what exactly is this blood pressure and why do the targets keep changing? Blood pressure is simply the pressure exerted by the blood when it flows in the arteries, which are tubes that conduct blood from the heart to every other part of the body. Since the pressure is not constant and changes with the heart pumping, the pressure as the heart is pumping is called systolic pressure and the pressure when the heart is relaxing is called the diastolic pressure. Blood pressure is vital to get blood to different parts of the body. The most susceptible organ is the brain, which sits on the top and therefore most affected by a drop in pressure. A significant drop in blood pressure can also cause a stroke due to a decreased amount of blood to the brain. High blood pressure, as you may expect, damages the arteries due to increased stress which in turn leads to strokes, heart attacks and kidney damage by affecting the arteries supplying these organs.
The history of hypertension, which is high blood pressure, is an interesting one. The earliest description of hypertension was an indirect mention in 2600 BC, when the author states that "with too much salt in the food, the pulse hardens". The pulse obviously increases in amplitude as the pressure increases. In 1628, William Harvey, an English physician, was the first to describe that blood was pumped into the arteries, and came back to the heart via different tubes called veins. For his efforts, the medical community labelled him as a nutcase. It took close to 200 years for Stephen Hales to first measure blood pressure and another 100 years when the sphygmomanometer was invented in 1896.
Treatment of blood pressure was controversial in the 20th century, best exemplified by a quote from Dr John Hay, who said “The greatest risk to a man with high blood pressure, lies in its discovery, because then some fool is certain to try and reduce it.” The first reports that blood pressure was harmful came not surprisingly from the life insurance companies, who realised the increased mortality in people with a blood pressure greater than 160/95. The medical field followed, and the first trial that reduced stroke with control of blood pressure was published in 1967.
The Joint National Committee (JNC) [US] was then constituted to provide recommendations for blood pressure control, and published its first report in 1977. Over the next four decades, there have been eight reports published. The latest guidelines published last year recommended a goal of less than 150/90, for those over 60 years old, and less than 140/90 for those younger. These are the current recommendations, and were met with controversy, as they actually increased the targets for treatment, especially in the above-60 age group.
The pharmaceutical companies have cashed in, with blood pressure treatment being roughly a $5 billion annual revenue generator. The JNC documents have financial disclosures of the committee members, which do raise some concern, and is fodder for the conspiracy theorists.
One of the pitfalls of current day medicine is that data from population studies are extrapolated to individual patients. This one-size-fits-all approach is one of the reasons that blood pressure trials have had such variable results. The problem is that individuals are unique and will tolerate medication and blood pressure levels differently. Each individual will need a tailored plan that suits him.
The blood pressure saga will continue as science evolves. Let us not forget Brecht’s words: “The aim of science is not to open a door to endless wisdom, but to put a limit on endless error.”