MMP9 and COVID-19: After adjusting for age, COVID-19 patients with delirium had significantly higher GFAP levels at day 3 [270.5 (148.0,375.0) pg/ml vs. 113.0 (70.9,196.0) pg/ml, p = 0.021] and higher MMP-9 levels [50.3 (43.1,13.2) μg/ml vs. 28.9 (17.9,47.9) μg/ml, p = 0.003] at hospital discharge (Fig. 2C, Additional file 3).