Interesting finding, but I wonder: did they allow those patients to opt-in to the aspirin regimen? If so, it could potentially be related to other confounding

Interesting finding, but I wonder: did they allow those patients to opt-in to the aspirin regimen? If so, it could potentially be related to other confounding variables -- eating healthier or avoiding certain chemicals or some such. Basically, allowing opt-ins suggests that people who do so could already be more vigilant about their health. If not, given the previous indication of benefits from an aspirin regimen, I wonder if there was an ethical concern in not giving it to all patients.