Joe Biden's deteriorating speech

Joe Biden's deteriorating speech I'm not American and this is not a political speech, but I've seen a lot of videos of Biden saying essentially nonsensical sentences and it's obvious ridiculed. While I'm not ignoring his old age and other factors that suggest actual mental decline, could stuttering also be a factor? As one who stammers, I've had to abruptly change my sentence struggle as I couldn't say one word or clauses, which can of course come out as nonsensical.