If you’ve been taking aspirin every day to lower your risk of heart attack, despite not having an existing history of heart problems, a new Harvard study suggests you’re not doing yourself any favors. In fact, it would seem that millions of people regularly taking low-dose aspirin without being advised to do so by a doctor are relying on antiquated advice.

Many doctors recommend a daily aspirin regimen for patients with a prior history of heart attack or stroke, or a significantly increased risk for those conditions. However, millions of perfectly healthy people, especially older adults, take aspirin daily because they believe it will decrease their risk of developing health problems in the future. That myth has since been debunked, but not everyone has gotten the message.

The study, which utilized survey data from recent years to paint a clearer picture of aspirin use by the public, shows that a huge number of people are taking aspirin when there is no clear medical benefit. An estimated 10 million people over the age of 70 with no prior history of heart disease still take aspirin daily as a primary preventative measure.

The American Heart Association walked back recommendations for daily aspirin use earlier this year, noting that people over 70 who don’t have heart disease should avoid daily aspirin. The update also clarified that daily aspirin use should only be considered for people between 40 and 70 who are at an elevated risk of developing heart problems, and only under a doctor’s advice.

Advice for those who have a prior history of heart attack or stroke has not changed, and aspirin is still recommended with the approval of a doctor.

The confusion is understandable, especially considering that for many years doctors recommended regular aspirin use for older adults even if they didn’t have a risk of heart disease. Now that more is known about the risks and benefits, doctors are trying to reverse the trend.