By Amy Norton
TUESDAY, April 18, 2017 (HealthDay News) -- Conflicting guidelines on statin use could leave about 9 million Americans unsure about treatment, a new study suggests.
Researchers estimate that if all doctors followed the latest guidelines from the U.S. Preventive Services Task Force (USPSTF) for the cholesterol-lowering drugs, the number of Americans aged 40 to 75 on statin medications would rise by 16 percent.
In absolute numbers, that would mean another 17 million statin users.
If that sounds like a big jump, consider what would happen if all doctors followed the advice of the American College of Cardiology/American Heart Association: Statin use would climb by 24 percent -- for an additional 26 million Americans on the drugs, the study authors estimated.
The difference between the two sets of guidelines leaves 9 million Americans in a statin "gray zone." So, which guidelines are "right"?
That's not clear, said study lead researcher Dr. Neha Pagidipati, who's with the Duke Clinical Research Institute, in Durham, N.C.
Neither set of guidelines has been wholly embraced by doctors, and each has their detractors, she noted.
"I don't think we have an optimal set of guidelines yet," Pagidipati said.
The aim of this study, she said, was to try to add some context to the issue.
Dr. Thomas Whayne is a professor of medicine at the University of Kentucky's Gill Heart Institute.
Whayne said the study performed a "statistical exercise," and doubted it will alter anything doctors or patients do.
But, he said, it does highlight concerns that the USPSTF guidelines could leave a lot of people untreated.
The USPSTF is a government-appointed, independent panel of medical experts. It regularly reviews scientific research and makes recommendations on health screenings and preventive medicine.
Last year, the task force came out with recommendations on which adults should consider using a statin for primary prevention -- that is, preventing a first-time heart attack or stroke.
The panel suggested statins be considered for people who: are between the ages of 40 and 75; have at least one major risk factor for heart disease or stroke -- such as diabetes or high blood pressure; and have at least a 10 percent chance of suffering a heart attack or stroke in the next 10 years.
Meanwhile, the heart groups' guidelines set a lower threshold: People aged 40 to 75 can start a statin if their 10-year risk of cardiovascular trouble is 7.5 percent or higher.
How do you know what your 10-year risk is?
Doctors can use any of several "risk calculators" that researchers have developed. The one from the heart groups considers factors such as age, sex, race, cholesterol and blood pressure levels, and smoking habits.
That risk calculator, however, has been controversial since it was unveiled in 2013.
Research has found that it can overestimate the odds of cardiovascular trouble. And some argue that too many people could end up on statins, Pagidipati noted.
On the other hand, there are critics who say the task force guidelines do not go far enough.
A study published last month estimated that one-quarter of black Americans who were eligible for statins under the heart groups' guidelines would not be under the USPSTF recommendations.
Those researchers worried that many black Americans at risk of heart trouble would miss out on statin therapy.
For the new study, Pagidipati's team used data on over 3,400 Americans in a nationally representative government health study.
The researchers estimated that if all U.S. doctors followed the task force guidelines instead of the heart groups' recommendations, about 9 million fewer Americans would be on a statin.
The findings were published online April 18 in the Journal of the American Medical Association.
Where does all of this leave patients?
According to Pagidipati, both sets of guidelines emphasize the importance of doctor-patient discussions. Risk calculations are just a starting point.
"At the end of the day," Pagidipati said, "providers and patients need to have an open, informed discussion of the pros and cons of using a statin."
Whayne agreed. In the real world, he said, treatment decisions come down to those discussions. He also doubted that many doctors are relying on risk calculators.
The "cons" of statins include the potential for side effects, including muscle pain. They have also been linked to a small increase in patients' risk of diabetes.
Whayne said muscle pain can often be managed by lowering the medication dose, or switching to a different statin.
Cost, he noted, is generally not a major issue, since so many inexpensive generic statins are available.