I wonder if the author is sure his hearing is actually getting worse or his perception is getting worse?
I once thought the same thing. tldr: Nope. My hearing is fine. Anxiety causes my brain, afaict, to always be on the lookout for threats. No sound was being filtered from my conscious. The perception was that I "couldn't hear". I could hear fine, but I couldn't filter out unimportant from important. The result is something that seems like bad hearing.
Taking anti-anxiety drugs solved the problem for me. Like magic I could hear fine. Conversations, even in noisy situations, became easy to perceive and follow.
I couldn't find any documentation on this at the time. The doctor didn't think much about the idea. I wonder if anybody else had the same experience?