Men are less verbal than women. Processing words is not easy for them all equally.

When training people who work with seniors, we are told to speak slowly, carefully, etc, because as people age they cannot follow fast talking.

This reminds me of the new show, Scandal. I watched the first episode on OnDemand yesterday.... after seeing the original person it is based on, featured on CNN morning show.
Boy did they talk fast. So I looked them up on IMDB and there is even a thread on their forum about not being able to follow the dialog. I watched episode 2 this morning with breakfast and already they are slowing down some. I suppose the target audience of this fascinating well done show is mostly over 40.

So if you are aware of sundowning, I won't go further with it.
But following verbal communication cognitively can be one sign of it, as well as general aging. I know for myself at my age, often less is more for me at times. But I am still more verbal and energetic than my husband, by far, who tends to be quiet most of the time.