Nearly 13m more adults in the US will be eligible for statins after new guidelines widened the criteria for use of the drugs to treat high cholesterol and prevent heart attacks and strokes.

Using data from the National Health and Nutrition Examination Surveys, a team from Duke, McGill and Boston universities found that 49% of all American adults between the ages of 40 and 75 could be recommended for statin therapy, up from 38%, under guidelines issued by the American Heart Association and based on the risk of developing cardiovascular disease, including stroke, within 10 years. This would equate to around 56m people on statins. Of the extra 12.8m people that the researchers identify, they said 10.4m would receive the drugs for preventative reasons and the biggest increase would be among healthy people aged over 60.

The US and the UK have followed similar guidance over statins and the National Institute for Health and Care Excellence (NICE), which issues drug guidance recently recommended doubling the eligibility for statins in the over 40s from those with a 20% risk to those with a 10% risk of developing cardiovascular disease.

Statins are drugs that can reduce LDL, or “bad cholesterol” in the body and have been shown to reduce the risk of heart attacks and strokes. But they also come with common side effects, including nosebleeds, nausea and muscle pains, and less common effects including dizziness and loss of sensation. This has led to questions over their use in people deemed at low risk of cardiovascular disease or heart problems. To complicate matters, a recent review of statin data suggested that people reported typical side effects even when they were only receiving a placebo: a phenomenon known as nocebo. The potential benefits of statins are also being widened: an early stage study published suggested that they could be helpful in treating advanced multiple sclerosis.

The Duke analysis, published in the New England Journal of Medicine, is likely to prove controversial as the eligibility criteria widens to a large, otherwise healthy population. While some argue that the benefits outweigh the risk, others, including doctors who have said they wouldn’t take statins, have said that worrying side effects are being effectively sidelined on a massive scale.

John Abramson, a leading heart specialist at Harvard University, has warned that patients are not being warned of the risks or about how common side effects are. He said that extending eligibility was foolish because much of the clinical data from statin trials was held from the public.

“The production and dissemination about the benefits and harms of statins has been turned over almost entirely to commercial interests, what we take for knowledge is designed to optimise the drug makers’ fiduciary responsibility to maximise shareholder profit,” he said.

Because we don’t know the overall effect of statins, not just their action on cardiovascular disease, Abramson said, this would instead “set back the goal of improving population health.”

“The net effect of treating approximately 100 people with 10-20% risk over the next 10 years with statins is not to reduce the overall mortality rate, but to exchange one heart attack or stroke for another serious illness,” he said. “And in the meantime, about 18% of the people will experience side effects.”

Despite the widening of the criteria, around 1.6m adults previously eligible would no longer be able to be prescribed statins. This group includes primarily younger adults who have elevated cholesterol but a low 10-year risk of developing cardiovascular disease.

The researchers used data on 3,773 participants between the ages of 40 and 75 in the NHANES study, which collects detailed medical information including cholesterol levels in the blood.

Michael Pencina, professor of biostatistics at Duke Clinical Research Institute and co-author of the study, said: “We sought to do a principled, scientific study to try to answer how the new guidelines might affect statin use, particularly as they focused eligibility on patients with an increased risk of developing cardiovascular disease."

Pencina said that although the team had anticipated that there would be an age split in the findings, the size of the split was a big surprise.

“By far the biggest group affected was people aged between 60 and 75,” he said. “In men, free of cardiovascular disease and not currently on statins, the number recommended in this age group increases from 30% to 87% and in women from 21% to 54%.”

Pencina said that while their study suggested the number of people that could go on statins would greatly increase, it did not mean that every eligible person would take up the therapy. “Recommendations are just that: recommendations,” he said. “These guidelines correctly call for a thorough discussion between the doctor and patient about the risks and benefits of statins. It’s not like everybody who meets the guidelines should all of a sudden go on statins.”

This article was originally published on The Conversation.