Baby aspirin vs. Adult aspirin

For the past 20 years, I have been taken  baby aspirin everyday to help prevent heart disease. I increased my dosage from one to two baby aspirin a couple of years ago because I heard one baby aspirin a day doesn't really do anything. I just read an article in the paper that said new studies show one or two baby aspirin a day isn't effective.They suggested anyone on aspirin therapy for heart disease prevention should take one "Adult" aspirin a day. I was under the impression that two baby aspirin a day were as effective as one adult aspirin but with less side affects. Are there  new studies that suggest baby aspirin therapy is no longer effective? I wonder if I've been wasting my time all these years on something that is not effective.

[CCF CARDIO MD - DLB]

Even though this seems like a simple question, the minimum effective dose of aspirin is still unclear. For patients without established heart disease who are taking aspirin, I recommend a baby aspirin. For patients with a previous heart attack, I recommend 325 mg. For patients with intermediate levels of cardiac risk, I usually recommend 2 baby aspirins.