Slurring his words has nothing to do with his stutter. Slurred speech is usually a symptom of an underlying medical condition. I am guessing a stroke. A speech/language pathologist (https://momshieb.medium.com/thank-you-thank-you-fellow-aging-karen-caren-91e1ea4681a4) is guessing he has Parkinson's.

I did a bit of research after I published this and discovered that Biden never had his 2022 physical. It keeps getting mysteriously postponed. First it was postponed until December 2022, then it was January 2023, and now it's supposed to happen on February 16, 2023. You know that I will be looking closely at the results! If, that is, he ever actually has the physical.