At what age does a person's sex drive start decreasing?

Waning Libido: Hi this is actually a very good and frequent question i get in my practice. I have found that as we age our libidos come and go, and at times there seems to be no sane explanation. But, libido is a higher functioning need, not as important as food or sleep. So, anything getting in the way such as stress, fatigue, depression or a number of other medical conditions can be blamed.