'Graham’s blue eyes lasered in on me. “This woman has untreated diabetes,” he said. “It’s caused her to have thousands of small strokes that have killed all these parts of her brain. That’s what’s causing her dementia.”

“I didn’t know it could do that,” I said—a response that revealed my ignorance. I’d never even looked up the symptoms of untreated diabetes; I had assumed that a patient would never grow this sick from a common and manageable disease.'

https://www.newyorker.com/science/annals-of-medicine/the-assumptions-doctors-make