My Dad has dementia. Of his symptoms, does that include sleeping more?

Sleeping a lot is very common in the later stages of dementia. Here is a link to a site that explains in detail the stages of dementia & what to expect during each:

https://www.dementiacarecentral.com/aboutdementia/facts/stages/

Best of luck!

Hopefully you will find this helpful:

https://www.agingcare.com/articles/warning-signs-of-dementia-to-look-for-139753.htm

But sleeping more could indicate any number of medical/health issues. He should still be seen by his doctor and given a cognitive exam, among a general check-up, and this symptom should be communicated to the doc.