The study is the first to explore the timing of aspirin intake among cardiovascular disease patients.
Low-dose daily aspirin is recommended for people at high risk of heart disease and for reducing the risk of recurrent heart events.
Aspirin thins the blood and makes it less likely to clot. The tendency for platelet activity to be higher peaks in the morning.
In the Aspirin in Reduction of Tension II trial, 290 patients took either 100 mg of aspirin upon waking or at bedtime during two 3-month periods. At the end of each period, blood pressure and platelet activity was measured.
Blood pressure was not reduced; however, bedtime aspirin platelet activity was reduced by 22 units (aspirin reaction units).
"Because higher platelet activity contributes to a higher risk of acute heart events, this simple intervention - switching aspirin intake from morning to bedtime - could be beneficial for the millions of patients with heart disease who take aspirin on a daily basis," said Tobias Bonten, student at the Leiden University Medical Center in the Netherlands.
The study was presented at the American Heart Association's Scientific Sessions 2013 in Dallas.