Results of the Studies (II)
What have we learnt so far?
The treatment with the two statins has caused a very significant decrease in LDL. CHD has also decreased, and other illnesses such as cancer and stroke have not been impacted. Never the less, mortality has not improved! Somehow, the decrease in CHD is offset by an increase in some other causes of mortality, in these studies!
However: in the ALLHAT paper, they combine their mortality results with results from 8 other large studies, and conclude that there is an average reduction in mortality by 14% (10% to 18% Margin of Error). Another recent study ("The Heart Protection Study" - Lancet, vol 360, p7 - this study was performed on people who had CHD related illnesses or diabetes) put the risk reduction at 13% using 40 mg simvastatin. (The Margin of Error was from 0.81 to 0.94). This demonstrates how difficult it is to obtain reliable results despite the many thousands of people who participated in all these trials. We also note that this 14% reduction pertains to the entire population of all the experiments. It does not tell us how this number changes for low-risk versus high-risk populations.
Is there a different way to look at the data? (see also our Risk Tutorial).
The mere fact that it is so difficult to determine any impact to the mortality rate as a result of taking statins, raises the question as to whether it is worth while to take them. Here are some aspects to consider:
1. Let us assume that you are a member of a group of 100 people. According to ALLHAT, the 6 year mortality rate was approximately 15%, so that you would expect on average, 15 people to pass away. if we reduce this rate (by 14%) by taking statins (15% minus 14% of 15%), we get a rate of 13% in round numbers. So if every one of the 100 people took statins for 6 years, we would expect only 13 to pass away.
2. Of course, we haven't actually "saved" the 2 lucky patients. The mortality probablity is increasing with every passing year, so that it is only a matter of time till the probability of dying while taking statins (at a later date) catches up with the probability of dying without taking statins, at the end of ALLHAT. To determine the "extension in time" until the "with statin" curve catches up with the "placebo" mortality curve, we assume a proportional relationship - if the risk is decreased by a factor X, the time it takes to get to the same mortality takes 1/X longer. Click here for details. This results in 11 months "extra" for 2 people out of the 100 that took statins.
3. In summary: without statins, an average of 15 people out of 100 would die in 6 years. With statins, an average of 13 people would die in 6 years, and an additional 2 people before the end of seven years!
What about side effects?
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A decision whether to take statins also depends on what side effects the statins have. If there were no side effects, one could decide to take statins solely on the basis of their cost. However, as we shall see in the next section, there is a significant chance of adverse reactions, that people who consider taking statins, should bear in mind.