Systemic arteries could, however, undergo structural and functional alterations due to degradative aging processes, extrinsic deleterious events, such as sleep apnea/intermittent hypoxia, or genetic deficiency in some components of the elastic fibers made of ≈90% elastin (= polymer of the precursor tropoelastin), ≈10% microfibrillar components, especially fibrillin-1, and several quantitatively minor components, although of major importance, such as lysyl oxidase (LOX), which is responsible for the cross-linking of tropoelastin [10]. Here, LOX is linked to sleep apnea syndrome.