Rio de Janeiro, Nov 14 (IANS): Obesity is the factor most associated with the development of endothelial dysfunction, a condition in which the blood vessels become unable to contract and relax adequately, increasing the risk of events such as heart attacks, thrombosis (blood clotting) and stroke in Covid-19 patients, finds a study.

Endothelium refers to the thin sheet of cells lining the walls of arteries and veins, as well as the inside of the heart.

Endothelial cells release substances that control vascular relaxation and contraction, and enzymes that regulate blood clotting and immune function.

"We characterised the patients in general and then set out to identify the factors that might modulate or intensify endothelial damage. The results showed that the key factor was BMI, followed quite a way behind by blood creatinine level, a marker of kidney function," said researcher Alessandro Domingues Heubel from the Federal University of Sao Carlos.

For the study, published in the journal Obesity, the research team analysed data from 109 patients hospitalised owing to acute Covid-19 but not in a critical condition.

Blood samples were collected shortly after hospital admission, and endothelial function was assessed non-invasively 72 hours later by the flow-mediated dilation (FMD) method, in which the diameter of the brachial artery is measured by high-resolution ultrasound before and after circulation is restricted in the forearm for a few minutes.

Besides FMD and BMI, the researchers assessed muscle health by measuring grip strength with a dynamometer and analysed blood levels of hemoglobin, leukocytes, lymphocytes, creatinine and platelets, as well as C-reactive protein, ferritin and D-dimer (markers of inflammation and coagulation).

To find the determinants of endothelial dysfunction in the study sample, the team used univariate regression and multiple regression.

Only high BMI and the level of creatinine were found to correlate directly with a decrease in FMD.

According to the researchers, each additional unit of BMI corresponded to a decrease of 0.19 per cent in FMD.

"In clinical practice, we find that obese patients have more cardiovascular events while they're hospitalised," the researchers said.

"Our study can help understand the mechanisms underlying this problem and why obesity increases the risk of progressing to severe Covid-19," they added.