The circadian rhythm of selected parameters of the hemostasis system in healthy people.
Level 3 - non-randomized controlled study
Prospective repeated-measures observational study in a single cohort of healthy volunteers
PubMed 31473402 · doi:10.1016/j.thromres.2019.08.015
What was done
Blood samples were collected from 66 healthy volunteers at 6-hour intervals over a 24-hour period (8 am, 2 pm, 8 pm, and 2 am) to assess circadian fluctuations in parameters of the coagulation and fibrinolytic systems, including platelet aggregation, platelet counts, APTT, PT, fibrinogen, PAI-1, PAP complexes, TAT complexes, t-PA, and D-dimers.
What was found
Coagulation activation predominated in the morning (8 am), characterized by increased platelet aggregation, prolonged APTT, and elevated levels of fibrinogen, PAI-1, PAP complexes, and TAT complexes. In contrast, circulating platelet count peaked in the afternoon (2 pm), accompanied by prolonged PT and increased levels of t-PA and D-dimers, reflecting progressive activation of fibrinolysis into the afternoon. Exact numerical concentrations, variance, and p-values were not reported in the abstract.
Why it matters
Demonstrating morning peaks in prothrombotic markers and afternoon peaks in fibrinolytic activity helps explain the established clinical pattern of increased morning incidence of acute cardiovascular and cerebrovascular events.
Limits
The study is limited by a modest sample size (n = 66) restricted entirely to healthy individuals, which may not reflect patterns in patients with baseline cardiovascular disease. Blood sampling occurred only four times across 24 hours (every 6 hours), providing coarse temporal resolution, and the abstract omits quantitative effect sizes and statistical parameters.
Cited by
- supports Platelet activity peaks in the morning, making platelets stickier and more prone to aggregating into clots.