Thirty percent of human population has a high blood pressure and everyone has a 90% risk to acquire it during
rest of
life. As a result, half of all human deaths are due to
major complications of high blood pressure, mainly stroke and heart attack.Medical scientists are fighting this life-threatening disease and they have gained some success. That is
development of several classes of antihypertensive drugs and definition of “normal” levels of blood pressure that should be maintained to reduce
risk of cardiovascular complications and death.
Is it a great success? Unfortunately not. Pharmaceutical treatment can not reverse
disease. The patient with developed arterial hypertension can only hope to reduce
risk of high blood pressure complications. How big is this risk reduction? Relative risk reduction is less than 25% during 2-5 years for all major cardiovascular complications. It is higher for stroke (36-45%) and less for heart attacks (10-15%). When all risks are combined,
relative risk reduction is close to 25%.
Be careful and distinguish absolute and relative risk reductions. Papers and pharmaceutical ads always present relative risk reduction which is more impressive. They even do not mention that it is “relative”. That is because
absolute risk reduction could be as much as 0.2-2.0%. Does not impress you, right? Let’s take a clinical trial where 0.6% and 0.96% of patients had had fatal stroke in
treatment group and placebo group accordingly. Absolute risk reduction will be 0.96% - 0.60% = 0.36%, however relative risk reduction will be as much as (0.96% - 0.6%)/0.96% = 37.5%! Looks much better! Absolute risk reduction 0.36% means that from one thousand patients taking medication during 3-5 years, three or four could be saved from fatal stroke. Clinical trials don’t say what will happen with those saved patients after 5 years. Presumably,
risk is postponed towards after 5 years period. Clinical trials also do not say which particular patients will be saved. It is like lottery, it could happen that 4 saved patients is just a difference between 44 saved and 40 preliminary died due to pharmaceutical side effects. Vioxx, Celebrex, Baycol are
known examples.
As you see everyone has to pay for this risk reduction not only by inconvenience and cost of pharmaceuticals, but also by
risk of unpleasant or life-threatening side effects. For
patients with high estimated risk (more than 10% during 5 years or more than 20% during 10 years) this price is considered to be a worth-while to pay.
Estimated risk is calculated by doctor. Taking
patient’s age and blood pressure level, plus
presence of risk factors, such as smoking, diabetes, high cholesterol, obesity, atherosclerosis and renal dysfunction, doctor can say that
risk for
cardiovascular complications of high blood pressure during 5, 10 or 20 years will be certain amount of chances For example, smoking woman, aged below 65, with abdominal obesity (waist more than 102cm) and blood pressure 140-179/90-109 mm Hg will have 15-20% absolute risk of all cardiovascular events at 10 years. Just add one more risk factor (diabetes or high cholesterol) and
risk goes up to 30%. This is high risk and
treatment is definitely required.
For
patients with initial stages of hypertension and low risk
balance between benefits and drawbacks of antihypertensive drugs is not established. There are three reasons for being reluctant to start taking antihypertensive drugs without having 10% estimated risk of cardiovascular complications.
Reason one: absolute risk reduction from, let’s say, 7 % to 5 % does not look sufficient to justify long-term expensive, unsafe and inconvenient treatment.
Reason two: even if we decide to operate
relative instead of absolute risk reduction, we CAN NOT do this, because available clinical trials have demonstrated risk reduction for
high risk patients and we can not extrapolate these results to
low risk patients. Clinical trials on low risk patients were not performed and we do not know if
harm of
treatment overbalances
benefit.
Reason three: negative side effects of antihypertensives are well known and include metabolic, lipid and hormonal disturbances including development of diabetes. We know that for
high risk patients (read - low life expectancy)
danger from
drug treatment is less than
benefit, but we do not know and we can not know without 20-30 years studies if it is
case for
low risk patients.