Can you cover his cage once he's in for the night so it's more cave-like? Try that? And maybe an extra walk before bed, and a peanut-butter filled Kong ... how long has this behavior been happening?

Would it be possible to maybe keep him in the kitchen inside at night? A bed in a corner, and he'd be inside with less distractions, and may feel less anxious. If you could confine him to the kitchen, there's usually no carpet to catch dog dander, etc., ... and you could move his bed outside in the morning when he goes out, to keep the dander outdoors ...

I just suggested a vet visit because of his age ... things can start going wrong with older dogs, and it might be worth a check.