David Cassidy is just one more of those who appear "bigger than life" to have been diagnosed with dementia.  The Huffington Post article does a very good job educating us about some of the various types of dementia (there are approximately 72 types, some which are reversible).
I'm posting it for your convenience:  ​http://www.huffingtonpost.com/entry/david-cassidy-has-dementia-heres-what-that-means_us_58adc2d5e4b04a0b274ecb4f

​David, we wish you well...and we think we love you....