Understanding a dementia diagnosis in the wake of Jack Hanna’s family announcement In an open letter from his family, they say Jack Hanna was diagnosed with dementia and it’s now believed to be Alzheimer’s Disease. Author: Lindsey Mills Updated: 11:12 PM EDT April 7, 2021 COLUMBUS, Ohio — Alzheimer's Disease is the sixth leading cause of death in the United States and there is no cure, according to the Alzheimer's Association of Central Ohio. It is a devastating diagnosis for anyone to receive – and for their caregivers. And it’s one that the family of Jack Hanna now knows all too well. On Wednesday, his family revealed in an open letter to the community that Hanna was diagnosed with dementia and it’s now believed to be Alzheimer’s Disease.