Study author Tobias Bonten of the Leiden University Medical Center in the Netherlands studied 290 patients with heart disease who were already taking aspirin. Study participants took 100 milligrams of aspirin in the morning or at bedtime during two three-month periods. At the end of each period, they measured participants' blood pressure and platelet activity, USA Today reported.
Aspirin thins the blood and makes it less likely to clot. Blood platelets are a key component of clotting, and the tendency for platelet activity to be higher peaks in the morning.
Low-dose daily aspirin is recommended for people at high risk of heart disease and for reducing the risk of recurrent heart events.
The researchers found platelet activity was lower in people who took aspirin at bedtime compared to those who took it in the morning, the study said.
The findings were presented at the American Heart Association's Scientific Sessions in Dallas.