Acute stress triggers a cascade of biochemical reactions that physically alter the composition of blood and increase the risk of clot formation. This conclusion was reached by researchers at the University of New South Wales. Their findings were published in the Journal of Physiology (JP).
In a randomized crossover study, eight healthy young men aged 18 to 30 participated. Each individual visited the lab twice, with a one-week interval between visits: one session involved quiet rest, while during the other, they had to complete the Trier Social Stress Test. This test required the participants to prepare a speech and deliver it in front of a camera and a stoic panel. Immediately afterward, they had to verbally count backward by 17 from 2003, restarting each time they made a mistake.
Blood samples were collected before and after both sessions. The researchers were particularly interested in measuring free radicals and analyzing the structure of developing blood clots.
Following the stress test, two changes were observed simultaneously: the level of free radicals increased, and the structure of the clots was completely transformed—they became larger, denser, and richer in fibrin, the protein that forms the framework of a clot. After the period of quiet rest, the chemical composition of the blood remained stable.
Interestingly, blood viscosity did not change under stress, which disproves the theory of hemoconcentration. It turned out that stress influences the very quality and architecture of the clot through an oxidative mechanism.
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