As guys get older, it's normal for their libido to slowly go down. But while this is normal, it will happen to different degrees for different people. Most men, on the other hand, are still sexually interested in some way well into their 60s and 70s. Even though getting older is the main reason for this, a loss of libido can also be caused by other things. At the top of this list are things like fatigue, depression, illegal drug use, alcoholism, and high amounts of stress.