Which of these age-related disorders is related to loss of elasticity of the lungs and hypoxia: ?

It is called Sleep apnea.  

Sleep apnea is a more serious sleep disorder in which repeatedly breathing stops and starts. You may have sleep apnea if you snore loudly, and you feel tired even after a full night's sleep, The signs and symptoms of obstructive and central sleep apneas overlay, most of the times making the type of sleep apnea more hard to determine. The most common signs and symptoms of obstructive and central sleep apneas.