Patients report more side effects when they know they are taking a statin than when don’t, according to findings of a recent study led by researchers at Imperial College London, funded by Pfizer, and published in The Lancet.

Clinical studies have shown that side effects are at similar levels in patients taking either a statin or placebo but, in the ‘real world’, it is estimated that as many as one fifth of patients may stop taking or refuse the drug for fear of reported side effects - which include muscle pain, cataracts, memory loss, erectile dysfunction and disrupted sleep.

Moreover, observational studies where patients were not ‘blinded’ as to whether or not they were taking a statin or a placebo have generated numerous reports linking cholesterol-lowering drugs with a variety of adverse events of side effects.

But the researchers believe such studies may be influencing patients to link some of their symptoms to statins, in what is being referred to as a ‘nocebo’ effect, in other words, “where a patient is taking a tablet, they know what they are taking, and they develop a side effect which has been associated with the drug, but it is not related to the actual chemistry of the drug,” explains Dr Ajay Gupta, study co-author, from Imperial’s National Lung Institute.

“Large randomised and blinded clinical trials have shown that statins are safe and effective in reducing the incidence of major cardiovascular events, yet many patients taking them outside of a trial setting complain of side effects,” explained Professor Peter Sever, from the National Heart and Lung institute at Imperial, who led the research.

“We wanted to explore why this might be the case, and whether someone who doesn’t know they are taking statins will still experience the side effects.”

The team analysed data from a large randomised clinical trial  - called ASCOT - which looked at lowering cholesterol in more than 10,000 patients in the UK, Ireland and the Nordic regions.

During the three-year study, patients received either a statin or a placebo but were not told which they were taking. At the end of the trial, patients were monitored for a further two years as part of a follow up, during which time they were aware of whether they were taking a stain or not.

The findings revealed that when patients didn’t whether they were taking a statin or a placebo, the number of side effects reported was similar in those taking the statin and those taking placebo. However, if patients were aware the were being treated with a statin, reports of muscle-related side effects in particular increased dramatically, by up to 41 percent.

The researchers suggest that the growing number of reports overstating the risks of statins could be impacting the number of patients taking them, potentially increasing their risk of heart attack and stroke in the long term.