Why so early?

Why has our elderly English Setter suddenly decided that it's great to get up at 5:30 every day? This is killing us!

I mean, even 6:30 would be okay, but 5:30 is ridiculous! I know she probably has a tiny old dog bladder now, but what is with this sudden clockwork early rising? It's not 5:35, it's not even 5:45... oh noooo, 5:30! The sun isn't even up. You can tell her to go lie down, and she will, for 30 seconds. Then it's pacepacepacepacepace. How can we get her to sleep in for an extra hour? She turns 13 next month and she's never done this before on such a regular basis.

The old dog farts we can deal with, but this is wearing us both out! Lucky she's so sweet...