Timing of aspirin intake did not affect BP

DALLAS — Aspirin intake at bedtime did not lead to reduced BP when compared with aspirin intake in the morning, but it was associated with greater inhibition of platelet reactivity during morning hours, according to data presented at AHA 2013.

Tobias N. Bonten, MD, of Leiden University Medical Center, the Netherlands, and colleagues conducted a randomized, open-label, crossover study of patients using low-dose aspirin for CVD prevention.

Previous research showed that taking aspirin at bedtime reduced 24-hour systolic BP by –5 mm Hg to –7 mm Hg compared with taking it in the morning, but those studies were of healthy participants, not those with CVD or at risk for it, Bonten said. In addition, previous research demonstrated that platelet reactivity is highest during morning hours, and thus so is the rate of acute CV events. However, it had not been studied whether aspirin intake at bedtime could reduce platelet reactivity during the high-risk morning hours compared with morning aspirin intake.

The researchers studied 290 participants (212 men) aged 18 to 75 years with baseline office systolic BP of 120 mm Hg to 160 mm Hg and baseline office diastolic BP of 70 mm Hg to 100 mm Hg. Half were randomly assigned low-dose aspirin (80-100 mg) to be taken at bedtime; the other half were assigned the same regimen to be taken upon awakening in the morning. At 3 months, the groups switched regimens.

At the end of the study, 263 participants could be analyzed for 24-hour BP and 136 could be analyzed for platelet reactivity.

No difference in BP

The 24-hour mean systolic BP for those taking aspirin at bedtime was 127.1 mm Hg compared with 127.2 mm Hg for those taking it in the morning (mean difference, –0.1 mm Hg; 95% CI, –0.9 to 1). The 24-hour mean diastolic BP for those taking aspirin at bedtime was 78 mm Hg compared with 79 mm Hg for those taking it in the morning (mean difference, –0.6 mm Hg; 95% CI, 0 to 1.2).

When plotting the BP of each group by the hour during a 24-hour period, the curves were nearly identical, Bonten said.

“We did not find any difference in BP [during the] day or night, whether the aspirin intake was upon awakening or at bedtime,” he said. “There were no crossover or period effects.”

Results were consistent across subgroups, including use of beta-blockers or angiotensin inhibitors, baseline systolic BP above or below 140 mm Hg and any use of antihypertensive drugs, he said.

Reduced platelet reactivity

However, those who took aspirin at bedtime showed reduced platelet reactivity in the morning compared with those who took aspirin in the morning (mean difference, –22 aspirin reactivity units; P=.001).

“This simple intervention could possibly reduce the excess of acute cardiovascular disease during morning hours, but future clinical trials are needed to assess clinical endpoints in order to draw a final conclusion,” Bonten said. – by Erik Swain

For more information:

Bonten TN. CS.03: Novel approaches to treating hypertension and atherosclerosis. Presented at: the American Heart Association Scientific Sessions; Nov. 16-20, 2013; Dallas.

Disclosure: Bonten reports no relevant financial disclosures.