I just had a phone conversation with an old friend, an older man who has Parkinson's. He used to do comedy and comedy writing, and he's a witty fellow. He got diagnosed with Parkinson's 20 years ago. He has taken up piano in the last few years, and I sent him a book of simple but well-arranged jazz standards. Apparently he submitted three videos that he had taken of himself playing piano to his doctor. They are from 2016, 2017, and 2020. He and the doctor both agree that in each succeeding video, his jerky Parkinson body movements are less. My friend feels that his daily piano practicing has not only improved his sight-reading, but his illness.
I'm no expert, but I'm interested in plasticity of the brain, and I've been reading Dr. Sanjay Gupta's book "Keep Sharp" about brain health. These things interest me: Music, various forms of health, music's effect on them, and brain plasticity.
I make music because I love it and am compelled to, but it's fascinating to hear about possible positive side-effects.