Since the 1980's, many Americans have turned to low-dose aspirin as a way to prevent heart attacks and strokes.
"That all of a sudden became engrained in our culture," said Dr. Nicole Lohr, of Froedtert Hospital and the Medical College of Wisconsin. "But we didn't have a lot of scientific evidence for what we were doing."
A National Health Interview Survey found up to 29-million people across the United States are currently taking aspirin but shouldn't be under new guidelines.
Those guidelines, from the American College of Cardiology, now recommend taking low dose aspirin as a way to prevent heart problems only in "select adults 40 to 70," who are "at higher Atherosclerotic Cardiovascular Disease risk but not at increased bleeding risk."
That's because aspirin prevents blood clotting cells in your body from sticking together, according to Lohr.
That can be a problem in older adults who are at an increased risk of falling.
"If your blood is thinner, you're going to bleed more. If you're bleeding more, that translates to a higher likelihood of dying," Lohr said.
"So it becomes a conversation with your doctor: is your risk of a heart attack or a stroke greater than your risk of bleeding?" she added.
As for people under 40, Lohr said clinical trials found there was not enough evidence to show that low dose aspirin could prevent heart problems in that group.
She also reiterated people at an increased risk of heart problems - either through previous health issues or with risk factors like high cholesterol or high blood pressure - should continue to take low-dose aspirin. Lohr thinks that should be the case even if a patient is over 70-years old.