If we could talk, I'm sure you'd admit that nothing will be gained by burying your head in the sand (so to speak) and refusing to face this problem honestly. After all, if you truly love your wife you want what's best for her -- and right now the best thing is to find out what her problem is, and get treatment for it.
The most important thing I can tell you, however, is that God knows what you're going through, and He wants to help you. God doesn't abandon us when old age comes upon us! As I've grown older, I've taken great comfort in God's promise to Isaiah: "Even to your old age and gray hairs I am he, I am he who will sustain you. I have made you and I will carry you" (Isaiah 46:4).
Does this mean God will take away all our problems, even as we grow older? Sometimes He may -- but more often He gives us strength to endure them. He also gives us hope for the future -- the hope of heaven. Whenever problems come into our lives, we need to learn to look beyond them to the glory God has promised us in heaven.
Don't fear the future, whatever it holds for you and your wife. Instead, know that Christ will be with you every step of the way. Commit your life and your future to Him. Then trust His promise every day: "I am with you always, to the very end of the age" (Matthew 28:20).