With regard to worse outcome and higher mortality of COVID-19 in older patients with diabetes mellitus or cardiovascular disorders, PDE4 inhibitors possess an advantage as they are able to increase a PDE4 activity in elderly, to reduce a body weight, to improve an insulin sensitivity [219], and to prevent adverse cardiovascular events of nonselective PDE inhibitors (xanthines) [220]. Here, PDE4A is linked to diabetes mellitus.