No, but if someone who is clearly losing it (and if you doubt that is the case, watch a side by side of Joe from 5 years ago, and now) has a good day half hour I don't assume he "discovered a cure for Alzheimers"
I don't have a problem with anyone using a teleprompter (in fact I'd prefer Trump stuck to his more), but you are trying to use this speech as evidence of Joe Biden's cognitive abilities, so the question of whether he is reading off a prompter is very much relevant
I'm not using this speech to prove that he's cognitively normal, just saying that it doesn't prove that he's not.
And it's not just this speech. What's been posted above are clips of a few seconds from much longer speeches, and he seems quite normal to me. What's clear is that the video-manipulator looked through 60 minutes of a speech to find 25 seconds that could be spliced together to make it seem like he's losing it. The complete videos don't resemble those clips.
I hear several things in his speech:
1, he grew up with a stutter, and still has to concentrate on controlling it.
2, he often starts a sentence, then gets excited and starts a slightly different sentence. Many people do this in natural conversations... We just don't do it in public where it's recorded.
3, he's got something of a Scranton accent, and I think that explains him saying Commnity College instead of Community College, as shown in the video. Some Americans think New Yawkers sound ignorant too.
4, he sometimes forgets a word, or a name, or uses the wrong word. Most people notice themselves doing this, especially after they reach their 50s. It's a natural part of the aging process, not necessarily indicative of dementia. We age gradually, and, as you say, if we're observed at intervals of 5 years, those gradual changes become obvious. Our speech slows down, we take longer to remember a word.
As far as I know, physicians don't diagnose dementia based on ability to speak with or without a teleprompter. But we can ask for their opinion of him. Here are evaluations from two of them:
There are no independently verified medical records available that measured and documented the cognitive functioning of Biden. However, his appearance on the campaign trail during the past year suggests that he is currently operating at an exceptionally high level. He is likely to pass the common screening tests for dementia like the mini-mental status exam (MMSE) and MoCA with a perfect score, but these tests would not be predictive because they’re only screening tools used to determine whether a full diagnostic assessment is required. His stuttering and speech reaction time is typical at his age and are not indicative of cognitive decline. The Framingham Heart Study estimates that in the general population, the risk for Alzheimer’s disease is around 10% at age 82 (Biden’s age at the end of his first term). Since Biden (and Trump) do not have dementia currently the risk is significantly lower.
Biden is a life-long stutterer and he admits that when fatigued, he can struggle with speech fluency. A stutter can be a lifelong articulation disorder that says nothing about cognitive functioning.
https://www.icaa.cc/media/presidential_lifespan_and_healthspan-draft_for_release_1.pdf