Dr. Barak Gaster, an internist at the University of Washington School of Medicine, had spent three years working with specialists in geriatrics, neurology, palliative care and psychiatry to come up with a five-page document that he calls a dementia-specific advance directive.

“The standard advance directives tend to focus on things like a ‘permanent coma’ or a ‘persistent vegetative state,’” Dr. Gaster said. “Most of the time, they apply to a person with less than six months to live.”

Although it’s a terminal disease, dementia often intensifies slowly, over many years. The point at which dementia patients can no longer direct their own care isn’t predictable or obvious.