How Strong is the Science?
At the Statin Answers website we report science and base the information on this website on the best science we can find. Not all scientific reports are equal and some make news with results that contradict the status quo, but the quality of the research is sketchy. Scientists and epidemiologists look at evidence that can include experiments on animals and humans, and at observations of patients who take the medicines in question.
Bigger studies (i.e. those with more patients and/or covering longer periods of time) generally provide stronger evidence that smaller ones just because of the laws of statistics. Large and longer studies are expensive and often impractical even if money were available. Further, some experiments and studies are set up better – with better controls and procedures – than others, so the results from the well-designed studies are more believable.
Studies of the efficacy and side effects of statins include experiments and observations. Experiments – often done to test treatments – often involve testing the differences in patient outcomes between patients who receive a treatment versus those who do not. Another common experiment compares patients receiving a new treatment versus those receiving an older, established treatment. There are challenges for the researchers in getting good data – patients drop out, misrepresent facts, or do not understand what the researcher is looking for.
Observational studies usually follow patients through their time on a medicine. In the case of statins which are taken for the long run, the studies can last years. Researchers check in with patients on a set schedule to monitor the signs and markers under question. Sometimes observational studies are backwards-looking, and patient memories and medical records are used to try to figure out relationships among lifestyle habits, diet, medication, disease, and other factors.
Experiments include randomized clinical trials (RCTs) and controlled clinical trials (CCTs). A CCT is a more general term for a clinical study between two groups. Patients in one group get the treatment or therapy of interest. The other group (the control group) gets no treatment or a placebo, or another treatment.
RCTs imply that patients are assigned to groups randomly. The patients agree to participate in the study but they do not get to choose whether they are in the treatment group or the control group, and in most cases do not know which group they are in.
Some experiments are "double blind". That means neither the patients nor the investigators know which patients are getting the treatment under investigation. Although difficult to design and execute, RCTs provide the strongest evidence on treatment efficacy, and all other things being equal.
When a regulatory agency such as the US Food and Drug Administration looks at a new medicine to consider whether it should be approved for sale and distribution, they consider the quality and quantity of evidence. For something like a new drug approval, RCTs will almost always be required or expected. Evidence for treatment guidelines can often rely on less robust evidence.
Formal observation studies include cohort studies and case-control studies.
A cohort study is an observational study but one in which the data is approached in a way so as to simulate an experiment to some extent. These studies often take historical data about patients or follow them over a period time. The word cohort indicates a group of people with something in common such as a shared experience in their past, same age, etc.
Case-control studies look at two populations with different attributes in some area of interests compared. The analyst then attempts to figure out (or make an argument for) what in the past produced the difference. For instance, if we had two groups of people in their 80s – one with dementia and one without – and we knew their sleep habits when there were younger, we could try to see if there was a difference between the sleep habits of the two groups and develop evidence that sleep affects the risk for dementia.
Statins have been used for decades now by millions of people and there is a wealth of all types of evidence about how effective they are and whether they produce side effects.
In considering a question, problem, issue - you have to look at available evidence – which may be contradictory – and make an assessment of the evidence. It is not always easy, but this is where experience in weighing evidence and drawing conclusions – and in knowing how firm your conclusion is – plays a part.