Morning increase in platelet aggregability. Association with assumption of the upright posture.
Why the study?
Does the assumption of upright posture cause the morning increase in platelet aggregability in normal subjects?
Population
16 normal subjects
Comparison
Normal morning activities divided into three… vs Control day of delayed arising
Follow-up
4.5 hours (8 AM to 12:30 PM)
Authors
Discussion
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Implication
Posture, not awakening, may drive morning platelet changes tied to MI peaks; hypothesis-generating, needs clinical validation.
Key Points
- To identify which morning activities increase platelet aggregability in normal subjects.
- Measured platelet aggregation in 16 normal subjects during activities of awakening, upright posture, and ambulation.
- Blood samples were collected before and after each activity to assess platelet aggregability.
- Compared results with a control day of delayed arising.
- Platelet responsiveness to adenosine diphosphate and epinephrine increased significantly after assuming an upright posture (the lowest agonist concentration for aggregation decreased).
- Plasma epinephrine and norepinephrine levels rose significantly after standing up, correlating with increased platelet aggregability.
- No significant changes in aggregability or hormone levels were observed on the control day.
Structured PICO
Does the assumption of upright posture cause the morning increase in platelet aggregability in normal subjects?
P
Population
16 normal subjects
I
Intervention
Normal morning activities divided into three isolated components: awakening (8 AM), assumption of upright posture (9:30 AM), and ambulating (11 AM)
C
Comparator
Control day of delayed arising (subjects remained supine until 12:30 PM)
O
Outcome
In vitro platelet responsiveness to adenosine diphosphate and epinephrinesurrogate
The morning increase in platelet aggregability, which may contribute to the morning peak in myocardial infarction and sudden cardiac death, is specifically associated with assuming an upright posture rather than just awakening.
Cite This Study
Brezinski et al. (1988) studied this question.