I am 81 and only just recently stumbled into this. The line that jumped out at me in Nadia's post is "As far as I can remember, going back, I never had good visualization." I've been trying to remember not just what I could visualize in the past, what I remembered in the past and what I did not remember in the past. For example, I remember at the beginning of 8th grade discovering that I could not remember anything that had happened in 7th grade. I had no idea that other people could really see things in their "minds eye". and assumed that it was a poetic metaphor until recently when I read about aphantasia. But I do have a memory of not being able to memorize and of forgetting experiences. But I don't remember ever having a clear idea of what sort of memory was "normal" any more than I knew that most people can see an apple in their mind.

I've seen reference to an article that raises the hypothetical question of aphantasia having a role in diagnosing neurogenerative diseases. However, I'm not sure that any correlation between aphantasia and Alzheimer's disease has actually been established. But there is a paper from Hungary that evaluated distributions of vividness of visual imagery in populations divided into different age groups. You can find a link to a video presentation on the subject as well as a link to the published paper here: https://aphantasia.com/video/aphantasic-with-age/ The paper shows a decrease in vividness of visual imagery between younger and older age groups. This was a population study, not a longitudinal study that followed the same individuals over time to evaluate changes. So there definitely are limitations with respect to providing an answer to your question about whether aphantasia can get worse.