Statins do not appear to cause muscle pain, despite many patients citing the side effect.
The cholesterol-lowering drugs are widely prescribed to prevent heart attacks and strokes in at-risk individuals.
Although often life-saving, statins have developed a bad reputation for causing nasty side effects, with many patients refusing or coming off the medication over concerns they may be causing intolerable muscle pain.
Feeling hard data to support this was lacking, scientists from the London School of Hygiene and Tropical Medicine (LSHTM) analysed 200 patients who had recently stopped taking statins due to muscle symptoms, or were considering doing so.
The patients received a statin or placebo tablet at different times over six two-month periods.
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Results reveal there was no difference in self-reported muscle pain, tenderness, stiffness or cramping when the same individual took the active drug or a sugar pill.
Two-thirds of the patients who completed the study said they would then restart, or continue with, their statin treatment.
Statins are "remarkably effective", according to study author Professor Liam Smeeth.
A study review has previously found "around one in every 50 people who take the medicine for five years will avoid a serious event, such as a heart attack or stroke, as a result".
Statins have repeatedly been shown to be safe, with any severe side effects being rare.
The jury was out, however, when it came to the prevalence of milder adverse events.
Muscle symptoms have been flagged in lower-quality clinical trials, prompting many to discontinue the treatment, which then raises their risk of heart disease, the LSHTM scientists wrote in The BMJ.
To learn more, the team analysed 200 patients – average age 69 – from 50 GP practices across England and Wales.
The participants were given a course of the statin atorvastatin and placebo tablets, with both the individual and their GP being unaware what the patient was taking at any one time.
Adherence was high, with at least four in five (80%) of the patients reporting they took their pill "every day" or "most days".
At the end of each two-month period, the patients rated their muscle symptoms on a scale of zero to 10.
"The use of each patient as their own control in the trial provides a powerful way of distinguishing the effect of a statin from that of taking a [placebo] pill," said Professor Sir Nilesh Samani from the British Heart Foundation.
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The results reveal there was no difference in muscle symptom scores when a patient took a statin or a placebo.
There was also no difference in how any muscle symptoms affected a patient's quality of life, like their sleep, mood or ability to walk.
Eighteen (9%) patients withdrew from the study due to intolerable muscle symptoms while taking a statin. This is compared to 13 (7%) withdrawals while on a placebo; not a statistically significant difference.
Muscular aches and pains are common among older people, which patients and doctors may mistakenly blame on statins, according to the scientists.
Widespread reports of statin-induced side effects may also cause patients to attribute any symptoms to the drug, in the so-called nocebo effect.
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"I often encounter people who have a firmly held view that statins cause muscle pains even when they haven't taken these medications themselves," said cardiologist Professor Tim Chico, from the University of Sheffield.
"I hope this study may help change this view and make them willing to try such an 'experiment'."
The LSHTM scientists stressed only one type of statin was tested in the study, at the "standard" 20mg a day dose. A patient's pain score may also have been affected by any previous treatments, they added.
Nevertheless, the trial was large and "well-designed".
The scientists hope similar research will be carried out for other statins at higher doses, as well as additional medications that are commonly associated with side effects.
"The patients in the study were willing to participate and take statins again," added Professor Chico.
"This means this group may not be completely representative of all those who believe they experience side effects with statins, as anyone who refused to take statins ever again would not have been recruited."
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