2nd Degree Heart Block / Mobitz 1

What causes 2nd Degree Heart Block / Mobitz 1?  Or why is usually detected later in life and not when a person is younger? I my case, found it when around 54 bday, at a general physical check up and talking to the physician about some pressure on the chest. I have alway been very athletic; marathoner, triathlete, swimmer, biker. Diagnosed with 2nd Degree Heart Block / Mobitz 1. Never, felt anything the year before, it just showed up !!!!  

[Jerry_NJ]

Heart rhythm problems increase with age, I was first diagnosed with Atrial Fibrillation at age 58, just came on and while not a marathoner, I was a regular jogger and aerobic exercise person.  

There can be many causes, but I think for most of us it is an accumulation of a life time of viruses, and other infections and the general wear-and-tear on our bodies as they go through the slow-down stages of aging.  Not a happy thought, but that's what I think.

I am not familiar with the treatment, but assume/home you are under the care of a cardiologist.