More than 11 million Americans may have incorrect prescriptions for aspirin, statins, and blood pressure medications, according to a new study.
Researchers based their findings on an updated set of calculations — known as pooled cohort equations, or PCEs — used to determine the risk of a heart attack or stroke.
The PCEs are the foundation for cardiovascular-disease-prevention guidelines in the United States. They help physicians decide whether to prescribe aspirin, blood pressure, or statin medications, or some combination of these, by estimating the risk a patient may have for a heart attack or stroke.
Most physicians calculate a patient's risk using a PCE web calculator or a smartphone app; the equations are also built into many electronic health records so that a patient's risk is automatically calculated during an office visit.
But there has been debate over whether the PCEs are based on outdated data and therefore putting some patients at risk for over- or under-medication.
"We found that there are probably at least two major ways to improve the 2013 equations," says Sanjay Basu, assistant professor of primary care outcomes research at the School of Medicine at Stanford University and a core faculty member at Stanford Health Policy.
"The first was well-known: that the data used to derive the equations could be updated."
For example, he says, one of the main data sets used to derive the original equations had information from people who were 30-62 years old in 1948, and who would therefore be 100 to 132 years old in 2018 — that is, likely dead.
The older equations were often estimating people's risk as too high, possibly by an average of 20 percent across risk groups.
"A lot has changed in terms of diets, environments, and medical treatment since the 1940s," says Basu, lead author of the study in Annals of Internal Medicine.
"So, relying on our grandparents' data to make our treatment choices is probably not the best idea."
Furthermore, the researchers found that the old data may not have had a sufficient sample of African Americans. For many African Americans, physicians may have been estimating the risks of heart attacks or strokes as too low.
"So while many Americans were being recommended aggressive treatments that they may not have needed according to current guidelines, some Americans — particularly African Americans — may have been given false reassurance and probably need to start treatment given our findings," Basu says.
For their study, the researchers updated the PCEs with newer data in an effort to substantially improve the accuracy of the cardiovascular risk estimates.
A second improvement to the equations, the authors found, was to update the statistical methods used to derive the equations.
"We found that by revising the PCEs with new data and statistical methods, we could substantially improve the accuracy of cardiovascular disease risk estimates," the authors write.
Researchers from the University of Michigan, the University of Washington, and the University of Mississippi also contributed to the study.
Grants from the National Institutes of Health and a Stanford graduate fellowship supported the research, as did Stanford's medicine department.