What is sundowning vs dementia?

Sundowning is a: Symptom that can occur in dementia patients. It refers to misperceiving the environment or outright halliucinations whch usually occur at or after sundown, hence the name. Dementia is a degenerative illness which effects the brain and inhibits a person's ability to function.

Can have both: Sundowning can be part of dementia. It is worsening of mental function at night. Here's a good resource on the topic. http://goo.gl/wx7q8.