TREATMENT OF HYPERTENSION CAN BE TRICKY
How low should you go with blood pressure readings?, write Dr. Zoe Oliver & Dr. Eddy Lang.
More than seven million Canadians suffer from hypertension, and many take multiple medications to bring their blood pressure down to normal. Left untreated, hypertension puts pressure on our major organs, possibly leading to heart attacks, strokes, heart failure and kidney disease, among other ailments. But many of the medications used in treatment have sideeffects, and interact with other common medications.
Consider the example of a 79-year-old diabetic man who lives at home alone. He is already on one medication for hypertension, and his doctor decides to add in another one. Getting up in the middle of the night to go to the bathroom, he becomes dizzy, presumably from a drop in blood pressure. He falls and breaks his wrist. Suddenly, he can’t cook or bathe on his own, and his quality of life is significantly diminished. Was the better blood pressure control really worth it, or is there a point at which the risks of treating high blood pressure exceed the benefits?
The first stop in the management of high blood pressure is usually lifestyle change, in the form of adequate exercise, a healthy diet, and moderate alcohol and sodium intake. But when this is ineffective or impractical, health professionals often need to introduce medications.
A blood pressure reading consists of two numbers with a slash between them, for instance 180/110. The first number is called the systolic blood pressure, and the second is the diastolic blood pressure. Both measure the pressure in the body’s arteries, which are the vessels carrying oxygen and nutrient rich blood to our organs. The systolic pressure is measured when the heart pumps, while the diastolic pressure is measured when the heart relaxes in between beats. Previously, the goal for most people was less than 140/90. (And that means both numbers need to be less than their targets, not just the systolic or the diastolic). The diagnosis of hypertension is usually made over several office visits, or from home blood pressure monitoring.
There has always been a balance between blood pressure control and medication sideeffects; a balance which controversially tips in favour of more permissive targets with advancing age. Often, hypertension treatment can result in low blood pressure, light-headedness, and fainting. In those over the age of 75, who tend to be more frail and prone to falls, these side-effects can be particularly problematic. Complicating matters is the under-representation of the very elderly in research trials, making it more difficult to draw conclusions about relative risks and benefits of hypertension treatment.
But the SPRINT trial, reported in the June issue of the Journal of the American Medical Association, has helped us better define the ideal blood pressure for the very elderly. Over 2,600 American patients were randomly assigned to either intensive blood pressure control (a target systolic BP of less than 120) or the more conventional systolic target of 140.
Researchers originally meant to follow the patients for five years, tracking overall death rates as well as deaths specifically from strokes, heart attacks, and heart failure. However, the study was stopped almost two years early because clear results were already becoming evident — the group being treated more intensively was doing significantly better than the group assigned to usual care. The study regulators felt that it was unethical to continue if there already seemed to be an advantage to one approach.
At the time the study was halted, there was a 34 per cent mortality benefit with more intensive control, with a similar improvement seen in the combined risk of heart attack, heart failure and stroke. Episodes of low blood pressure were noted to be more common in the intensive-management group, but really harmful side-effects did not differ between the two groups. However, it’s worth noting that the rate of side-effects did approach 50 per cent for all of the study subjects.
While these appear to be compelling findings, it is worth noting that the scientific literature is full of examples of studies that were stopped early because it seemed that one treatment had an advantage only to be proved wrong with additional research. Still, these days, the rules for stopping a study early are fairly strict, so we can presume that the risk of a wrong conclusion is low.
Interestingly, 90 per cent of the medications used in the SPRINT study were generic forms of antihypertensives and not the new, costly medications featured in glossy pharmaceutical ads. This means that big bucks don’t need to go toward obtaining significant mortality benefit.
The SPRINT study could well have dramatic implications for the management of hypertension in the elderly. It challenges conventional wisdom, and could represent a healthy evolution in blood pressure management targets for those over the age of 75.