U.S. guidelines urging more adults who never had a heart attack or stroke to take a daily aspirin may not have convinced people to take these pills, a recent study suggests.

In 2009, the U.S. Preventive Services Task Force, a government-backed panel of independent physicians, advised men ages 45 to 79 and women ages 55 to 79 to take aspirin to prevent heart attack and stroke as long as they didn’t have bleeding disorders that might make the drug unsafe.

To see whether people in that age range took the advice, researchers examined data from 2007 to 2015 on aspirin use for almost 89,000 men and women who didn’t have bleeding disorders or other medical reasons to avoid this drug. Overall, only 43 percent of these adults took aspirin during the study period.

Even after researchers looked at how many risk factors people had for cardiovascular disease — such as high blood pressure, elevated cholesterol and smoking — the 2009 recommendations didn’t appear to boost aspirin use, researchers report in the Journal of the American Heart Association.

After 2009, aspirin use declined from 45 percent to 40 percent among people at low risk for heart attacks and strokes; from 66 percent to 62 percent among people at medium risk; and from 76 percent to 73 percent among high-risk individuals.

“There are many examples of preventive therapies that are underutilized and are minimally affected by publication of recommendation,” said lead study author Dr. Jeremy Van’t Hof of the University of Minnesota in Minneapolis.

“The challenge with any therapy for prevention is the fact that you are attempting to make a change in a patient who feels well with no manifestation of disease,” Van’t Hof said by email. “It is much easier to convince someone to treat a broken arm or a pneumonia because they can see and feel the problem.”

Last year, the task force updated its aspirin recommendations, advising adults aged 50 to 59 who have at least a 10 percent risk of having a heart attack or stroke in the next 10 years to take aspirin every day.

The American College of Cardiology provides an online risk calculator here: tools.acc.org/ASCVD-Risk-Estimator-Plus.

The advice doesn’t apply to people in their 60s because the bleeding risk increases with age, however, and the jury is still out on whether this approach makes sense for people under 50 or over 70, the Task Force concluded in its most recent recommendations.

Many patients who haven’t had a heart attack or stroke will see a primary care provider and not a cardiologist, and the new study findings suggest that many of these patients aren’t getting the message that they may benefit from aspirin, said Dr. Ying Xian, a researcher at Duke University Medical Center in Durham, North Carolina, who wasn’t involved in the study.

“What is surprising here is that many patients with intermediate cardiovascular disease risk did not take aspirin for no apparent reasons,” Xian said by email. “This represents a missed opportunity for heart disease and stroke prevention.”

One limitation of the study, however, is that it looked at health records from patients seen in primary care, which may not represent all people at risk for cardiovascular disease or capture patients who take aspirin without a prescription, Dr. Samuel Wann, a researcher at Ascension Healthcare in Milwaukee who wasn’t involved in the study, said by email.

Even so, the findings add to the evidence that aspirin is underused as a tool to prevent heart disease, said Dr. Gregg Fonarow of the David Geffen School of Medicine at the University of California at Los Angeles.

“Prior studies have also shown that release of guidelines or national recommendations alone is not sufficient to influence care or treatment of patients,” Fonarow, who wasn’t involved in the study, said by email. “To better ensure evidence-based, guideline-recommended, well calibrated, aspirin use, performance improvement systems need to be implemented in all care settings.”