An estimated 9.3 million fewer adults would receive statins if physicians adhered to recommendations from the U.S. Preventive Services Task Force (USPSTF) instead of guidelines from the American College of Cardiology (ACC) and the American Heart Association (AHA).

Lead researcher Neha J. Pagidipati, MD, of the Duke Clinical Research Institute, and colleagues published their results online in JAMA on April 18.

In 2013, the ACC and AHA released updated guidelines that based recommendations for statin therapy on the 10-year risk of atherosclerotic cardiovascular disease (ASCVD). The USPSTF, meanwhile, released updated recommendations in November 2016 that increased the estimated ASCVD risk threshold and required at least one cardiovascular risk factor before recommending statin therapy.

“Having multiple guidelines out there for cholesterol-lowering drugs can be confusing to physicians and patients,” Pagidipati said in a news release. “Until we get more definitive answers about the optimal approach, the best we can do is understand the pros and cons of each set of guidelines. Our study adds some of that context.”

For this study, the researchers identified 3,416 adults who were 40 to 75 years old and enrolled in the National Health and Nutrition Examination Survey (NHANES) from 2009 to 2014. The participants were excluded if they had a history of symptomatic coronary artery disease or ischemic stroke, had a triglyceride level greater than 400 mg/dL and had missing cholesterol and systolic blood pressure readings.

The median weighted age of the adults was 53 years old, while 53 percent were women and 21.5 percent were taking lipid-lowering medications.

The researchers noted that full implementation of the USPSTF recommendations would be associated with an incremental increase of 15.8 percent of adults receiving statin treatment. By contrast, full implementation of the ACC/AHA guidelines would be associated with an incremental increase of 24.3 percent of adults receiving statins.

They added that only 0.4 percent of adults would be recommended for treatment by the USPSTF but not by the ACC/AHA guidelines, but 8.9 percent of individuals in the primary prevention population would be recommended for statin therapy under the ACC/AHA guidelines but not under the USPSTF recommendations.

If the estimates are projected for the U.S. population, an estimated 17.1 million U.S. adults would receive a new recommendation for statin therapy based on the USPSTF recommendations and an estimated 26.4 million U.S. adults would receive new recommendations for statin therapy based on the ACC/AHA guidelines.

“Further exploration of those who are recommended to receive statins by the ACC/AHA guidelines but not by the USPSTF recommendations revealed that younger adults (4.9 percent of the primary prevention population) and persons with diabetes (2.5 percent of the primary prevention population) would account for much of this difference,” the researchers wrote. “Even though younger individuals have modest short-term CVD risk (7.0 percent over 10 years), approximately one-third would be expected to experience a cardiovascular event in the next 30 years. Given that half of all CVD events in men and one-third in women occur before age 65 years, reliance on 10-year ASCVD risk alone may miss many younger individuals who could potentially benefit from long-term statin therapy. Alternative approaches to augmenting risk-based cholesterol guidelines, including those that explicitly incorporate potential benefit of therapy should be considered.”

The researchers mentioned a few limitations of the study, including that they relied on NHANES data, in which adults self-report some of their data. They also could not determine the effects of new recommendations for adults currently taking lipid-lowering therapy and did not account changes in risk and treatment patterns over time. In addition, they assumed that treatment recommendation was the same as treatment initiation, which might not have been the case in all adults. Further, they acknowledged that some physicians have speculated that the ASCVD risk score overestimates risk in some subgroups.

“Even though younger people have a modest short-term risk of developing cardiovascular disease in 10 years, the risk escalates over 30 years,” Michael J. Pencina, PhD, a senior study author from the Duke Clinical Research Institute, said in a news release. “Half of all cardiovascular events in men and one-third in women occur before the age of 65 years, so reliance on 10-year risk could miss many younger people who could potentially benefit from long-term statin therapy.”