Malcolm Young,co-founder of AC/DC,died of dementia at age 64. I knew he had been ill for awhile but didn't know it was dementia. Took my son to his first concert to see AC/DC in January 1996. He was 9 years old and he still talks about it. 
https://m.huffpost.com/us/entry/us_5a0c94fbe4b00a6eece60d41?ncid=inblnkushpmg00000009
https://m.huffpost.com/us/entry/us_5a0c94fbe4b00a6eece60d41?ncid=inblnkushpmg00000009