Donald Trump is nearly 80 years old. While many older adults are highly functional, age can also come with cognitive changes that affect our ability to function well in complex settings. We are seeing that from Trump, as he uses his rallies and appearances to ramble, meander, and crudely lash out at his many perceived grievances. He also is notably refusing to give the public the ability to properly vet or scrutinize his capacities. Just last week, he backed out of an interview with 60 Minutes, and he is refusing to debate Vice President Harris again"both venues where the country might be able to more adequately assess his demeanor and fitness. As we saw in the first presidential debate, Trump is displaying irrationality and irritability. Notably, he ranted about migrants eating people's cats and dogs. This was widely debunked as untrue. In the limited opportunities we can examine his behavior, he's providing a deeply concerning snapshot. Given his advancing age"if elected again, he would be the oldest president in history by the end of his term"his refusal to disclose even basic health information is a disservice to the American people.