What neurological condition would cause a person to revert to child-like state and reverse sleep cycle? almost certain it is dementia

Dementia: Dementia is best evaluated by a professional. Memory problems/decline are often central to a diagnosis. The problem is that one can have memory problems for a number of reasons, and many memory problems are temporary. So, your doctor can assist you in determining the likely cause of your concerns. Note: symptoms of progressive dementias typically are not seen people younger than 65.

More information: You're correct, people with dementia may appear to be childlike and have changes in their sleep cycle. The only way to be sure is through medical and neuropsychological evaluation. Proper diagnosis is important. If it is dementia, there may be medications and other recommendations that can help address sleep and behavior changes.