Often time’s people confuse Delirium with Dementia because the symptoms can overlap. However, symptoms of Delirium are usually temporary and begin suddenly. The person may experience changes in level of awareness, extreme personality and or emotional changes, as well as confusion. The onset of Dementia symptoms usually progress slower and are permanent. A person with Dementia usually experiences an irreversible, physical change in the brain which makes the condition permanent. With that being said it is not uncommon for Dementia patients to experience Delirium as a result of medication, an infection or dehydration. Although delirium is usually temporary it can be dangerous if left untreated especially if it is caused by an infection or other serious medical condition. It is important to speak up if you believe your loved one seems more confused than normal because other people including medical personnel do not observe them on a daily basis. They may perceive their confusion as normal considering they do not have any other point of reference to serve as a comparison.
If you want to read more about dementia and delirium these websites may be of interest: