Effect of aspirin intake at bedtime versus on awakening on circadian rhythm of platelet reactivity. A randomised cross-over trial.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 25208590 · doi:10.1160/TH14-05-0453
What was done
A randomised, open-label crossover trial in 14 healthy subjects evaluated the effect of aspirin timing on circadian platelet reactivity. Participants took 80 mg acetylsalicylic acid either on awakening or at bedtime for two 2-week periods separated by a 4-week washout. At the end of each period, blood was drawn every 3 hours to measure COX-1-dependent (VerifyNow-Aspirin, serum thromboxane B2 [STxB2]) and COX-1-independent (flow cytometry CD62p expression, microaggregation) platelet activity.
What was found
VerifyNow platelet reactivity across the whole day was similar between intake on awakening and at bedtime (mean difference: -9 [95% CI -21 to 4]). However, bedtime aspirin reduced the morning peak in COX-1-dependent activity compared to awakening intake (mean difference VerifyNow: -23 Aspirin Reaction Units [95% CI -50 to 4]; STxB2: -1.7 ng/ml [95% CI -2.7 to -0.8]). COX-1-independent assays showed no effect from timing.
Why it matters
Taking aspirin at bedtime suppresses morning peak COX-1-dependent platelet activity better than morning administration, supporting further study of chronotherapy for cardiovascular protection.
Limits
Sample size was very small (n=14), participants were healthy volunteers rather than cardiovascular patients, the trial was open-label, and clinical cardiovascular events were not measured.
Cited by
- supports Platelet activity peaks in the morning, making platelets stickier and more prone to aggregating into clots.
- supports Blood pressure naturally surges and blood platelets exhibit increased stickiness in the morning as part of normal circadian biology.