A new worry

I am slightly worried that Addie might be showing signs of dog dementia. I know nothing about it and hope to find out more from Dr. Hirsch next Friday when both dogs go in to have their ears checked. The other night was the second time Addie has awoken me from sleep by barking, barking, barking. When I went to see what she was barking about, she was in the backyard barking at the doggie door. It made me think that she didn't remember that she could go through it anytime she wanted. She is only 9 years old but this was very weird behavior from her. And, as I said, this is the second time it has happened. The first time was several months ago. I hope this is something I don't have to face. She has been in such good health ever since she came to live with me.