Results of the Studies (I)
1. Do the medications result in reduced LDL ("Bad cholesterol")?
ALLHAT reports a reduction in LDL of 28% using pravastatin, compared to 11 percent with usual care. PROSPER reports a lowering of LDL by 34% compared to a placebo. ASCOT reports a 37% reduction after one year with atorvastatin. There is no question that these medications siginificantly lower the "bad cholesterol".
2. Do the medications result in less cases of CHD (Coronary Heart Disease)?
Quick Answer:ALLHAT reports that the Relative Risk of CHD resulting from pravastatin use, compared to "usual treatment" was 0.91. PROSPER, that also used pravastatin, but compares the result to a placebo, determined a Relative Risk of CHD of 0.81. ASCOT, using 10 mg atorvastatin, found a risk ratio of 0.64. So to provide a quick answer, the medications do result in a reduced incidence of CHD.
More details: We note that within the Margin of Error* (CL) ALLHAT reports that the Relative Risk of CHD resulting from pravastatin use, compared to "usual treatment" extends from 0.79 to 1.04. PROSPER, that also used pravastatin compared to a placebo, determines a Margin of Error from 0.74 to 0.97. ASCOT, using 10 mg atorvastatin, found (Margin of Error) Relative Risk between 0.50 and 0.83. These results could be combined into a single result, if they were measuring exactly the same thing (one type of medication compared to a placebo, for example), and we would get a range of 0.70 to 0.87, in which there is a 95% probability that the correct answer lies.
3. Do these medications help prevent other illnesses?
Quick answer: ALLHAT reports that the Relative Risk of stroke while using pravastatin was 0.91 PROSPER found no reduction for stroke, and a 1.25 risk increase for cancer . ASCOT found a risk reduction in strokes with atorvastatin of 0.73. In summary, there is no clear and systematic indication of any impact on other illnesses.
More details: ALLHAT reports that the 95% Confidence Level range for the Relative Risk of stroke while using pravastatin was 0.79 - 1.04. For PROSPER, the range is 1.04 - 1.51. ASCOT found a range of 0.56 - 0.96. Given these broad ranges that include both decreased risk (RR less than 1) and increased risk (RR greater than 1), there is no clear and systematic indication of any impact on other illnesses.
4. Do the medications result in reduced mortality over the period of the trial?
*Loosely speaking, this is the range in which the correct result is expected to be. For more details, please see our statistics tutorial.
ALLHAT found that all-cause mortality was statistically identical for the two groups (RR=1). PROSPER found a similar result (RR=0.97, ranging between 0.83 and 1.14 at the 95% CL). ASCOT obtained a slightly smaller value - RR of 0.87, but with a margin of error range from 0.71 to 1.06. So despite the reduction in CHD, overall mortality, based on these three experiments does not seem to be impacted !