Covid-19 and excess blood clotting: Several Chinese hospitals have reported that their patients are showing signs of excess blood clotting. In one, 5% of those hospitalized for covid-19 had a stroke (blood clot in the brain.) In another hospital, 25 random infected patients were screened for pulmonary embolism (clot in the lungs) and 10 came back positive. That's 40%. And more recently I saw a report of the bloodwork of hospitalized patients showing that most of them had excess clotting, although the degree to which this is so depends on the severity of disease. D-dimers are used as a marker of clotting in the blood, and the first graph here (A) shows levels in patients. Normal is <0.5. Many also had elevated levels of cardiac troponin, a marker of a heart attack or other damage to the heart tissue (which can be caused by a clot in the heart.) The second graph (B) shows these levels. This test is time-dependent. That is, the levels spike a certain number of hours after you have a heart attack. But clearly heart damage is a problem in some patients.

I suspect that this is at least part of the reason why deaths are higher in older people. Pretty much all of us are gradually building up atherosclerosis as we age, which means narrower passageways in the blood vessels. Older people are also more likely to form blood clots in general, and except in cases of clotting disorders, blood clots are uncommon in children.

Source of the graphs: https://www.thelancet.com/…/PIIS0140-6736(20)30566…/fulltext