On April 10, 2025, several hours after finishing a hike in Sedona, Arizona, Jan Anderson started repeating herself. “Did we hike this morning?” she asked. “Yes, we hiked,” said her husband, Steve Francks. “And you did really well.” But 15 seconds later, she asked the same question: “Did we hike today?” Anderson, 65, a retired finance executive, doesn’t remember any of it. She can recall what happened that afternoon only because her husband start…