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Outdated equations lead to incorrect prescriptions for cardiovascular conditions

A team of researchers has updated and improved the equations that guide prescribing decisions for physicians in the U.S. regarding cardiovascular risk.

Ever wonder how physicians determine what medication and dose you might need if you're at risk of a heart attack or stroke?

I recently learned that clinicians in the United States typically calculate this risk using a website or smartphone calculator based on equations approved by the federal government. Those numbers are also built into many electronic health records so a patient’s risk is automatically calculated during an office visit. But the datasets used to come up with those calculations are decades old — some dating as far back as 70 years.

That could leave as many as 11 million Americans at risk of taking the wrong dose of aspirin, statins and blood pressure medications, new research in the Annals of Internal Medicine suggests.

“A lot has changed in terms of diets, environments and medical treatment since the 1940s,” Stanford primary care physician and epidemiologist Sanjay Basu, MD,  senior author of the study, said in a Stanford Medicine press release. “So, relying on our grandparents’ data to make our treatment choices is probably not the best idea.”

Basu, a core faculty member at Stanford Health Policy, worked with a team of researchers to update the calculations known as pooled cohort equations, or PCEs, which were last updated in 2013.

The PCEs are the foundation for cardiovascular disease prevention in the United States. They help physicians decide whether to prescribe aspirin, blood pressure or statin medications, or some combination of these, by estimating a patient’s risk for a heart attack or stroke.

But Basu 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.

The researchers also found that the old data may not have had a sufficient sample of African-Americans and other groups. 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 told me.

The researchers have updated the PCEs with newer data in an effort to substantially improve the accuracy of the cardiovascular risk estimates. The National Institutes of Health — specifically the National Heart, Lung and Blood Institute — maintains and updates the cohort data and approved of their use for this study.

Photo by Mizianitka

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