Statins are medicines used to lower cholesterol levels (high cholesterol levels can lead to cardiovascular disease (CVD)). Statins are some of the most widely prescribed drugs in the UK but there are many reported side effects. These include muscle aches/weakness, joint pain, blurred vision, memory problems, feeling sick, and an increased risk of getting diabetes. The best type of study to examine the effects of statins are randomised controlled trials (RCTs): patients are given either statins or a placebo (a dummy drug having no effect) but they do not know which one they are taking. A number of RCTs and observational studies have been performed to date but the evidence around the safety of statins is conflicting. It is not always clear that it is the statins themselves causing the side effects from the observational studies, while the patients who take part in RCTs are not always representative of the rest of the population who are prescribed statins. New studies can be very expensive and time consuming and so we will use a statistical method called regression discontinuity analysis (RDA) using existing data which provides stronger evidence for a real relationship when a new RCT is not possible.
The evidence surrounding the safety of statins is conflicting despite a number of systematic reviews and meta-analyses. We will use a regression discontinuity analysis (RDA) to assess the effects of statins on both intended and unintended consequences. RDA is a statistical technique that allows for causal inference when a decision rule (such as being above or below a cut-off value on a continuous measure) is used to assign treatment. It is a quasi-experimental method that (like RCTs) reduces the effect of confounding of unobserved variables. The assumption being that patients lying just either side of the cut-off value are similar, in terms of observed and unobserved characteristics. Focussing on a small window surrounding the cut-off value should result in treatment assignment being the only difference between patients. We will therefore look at patient QRISK2 score as the exposure and our outcomes will include cardiovascular disease, future cholesterol levels and future QRISK2 scores (to determine efficacy of statins) and commonly reported side effects such as muscle pain and weakness, nausea and diabetes development (to determine safety). RDA is a novel method in clinical and epidemiological studies and it will provide insights into the causal effects of statins on side effects and also their efficacy.
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Kate Tilling - Chief Investigator - University of Bristol
Theresa Redaniel - Corresponding Applicant - University of Bristol
Lauren Scott - Collaborator - University of Bristol
Ruta Margelyte - Collaborator - University of Bristol
HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation