It seems hardly a week goes by when there isn’t an article in the press about the adverse effects of statins. Certainly not a week goes by when I don’t get asked about this by patients, or am told that they have stopped their statins because of something they have read. Are these articles accurate? Do these papers have your best interests at heart?

Statins are drugs that reduce the risk of heart attack and stroke by reducing your cholesterol. They are powerful, and have been so successful that they form part of the basic standard of care for any patient who has had a heart attack or stroke, or is at risk of one. For every 1mmol reduction in cholesterol they will reduce the chance of these things by 25%; in many of the trials the risk of such events is decreased by 40-50% by statin treatment.

Part of their controversy has come about from their success. As they have been more and more widely used, the medical view on the threshold at which they should be used in people at risk of heart attack and stroke has come down. In 2014, NICE (National Institute for Health and Care Excellence) recommended that the threshold for treatment with statins for people at risk of heart attack and stroke should come down to 10% over 10 years. This level of risk is only slightly more than the background risk in the general population and means that X million people should be treated with statins.

Some doctors, particularly general practitioners, felt uncomfortable about this and worry about the medicalisation of the population. They also say that as many as 1 in 5 patients cannot tolerate statins and they are generally the medical professionals who deal with the side effects. The commonest side effects are those related to muscles (aches and pains), but a huge variety of side effects are mentioned at times. It is partly these concerns that we see reflected in the press. In contrast, specialists in the field say that statins are incredibly well tolerated, safe and that the risk of side effects in trials is very low. So what is true?

The problem with the 1 in 5 figure about intolerance of statins is that it comes from observational studies – you look at a group of patients taking or doing something and see what happens. But in observational studies of these types, both the patients and their doctors in the trials know they are taking statins. If either or both of them expect side effects, side effects are more likely to happen. And we all know how common muscle aches and pains are as we get older!

This is known in medicine as the “nocebo” effect. The placebo effect is well known – if we are given a dummy tablet but believe it will do us good, many of us feel better. It has been known about and studied for a long time. The converse can also be true – a dummy tablet can make us feel worse – a nocebo. It is because of these effects that most medical treatments need to prove if they are effective in a “randomised, blinded” trial – the treatment is randomly allocated, and neither the participants nor the doctors running the trial know if they are taking the treatment or a placebo – both are blinded.

A recent analysis of a statin trial (Lancet 2017; 389: 2473–81) that had both a blinded and unblinded portion casts some light on this. The trial was blinded initially, and then continued with participants knowing if they were on a statin or not. The rates of adverse events were collected in both parts of the trial.

In the blinded part, the rate of adverse events related to muscle problems, erectile dysfunction and cognitive impairment were exactly the same for patients taking a statin and those taking placebo. Patients taking the statin were 31% less likely to report sleep disturbance. In the unblinded phase of the trial, when participants knew what they were taking, statin users were 41% more likely to report muscle related adverse events; there was no difference in the other adverse events.

So when we know we are taking a statin, we are more likely to report muscle side effects, but when we don’t know if we are taking a statin or a placebo, the rates of muscular aches and pains are exactly the same. Bear that in mind next time you hear someone blaming their statin for every side effect under the sun! You might even ask them if they slept better while they were taking it.