Dementia is not a specific disease.

It's an overall term that describes a wide range of symptoms associated with a decline in memory or other thinking skills severe enough to reduce a person's ability to perform everyday activities. Alzheimer's disease accounts for 60 to 80 percent of cases. Vascular dementia, which occurs after a stroke, is the second most common dementia type. But there are many other conditions that can cause symptoms of dementia, including some that are reversible, such as thyroid problems and vitamin deficiencies.

Dementia is often incorrectly referred to as "senility" or "senile dementia," which reflects the formerly widespread but incorrect belief that serious mental decline

While symtoms of dementia can vary greatly, at least two of the following core mental functions must be significantly impaired to be considred dementia:

•Memory

•Communication and language

•Abillity to focus and pay attention

•Reasoningand judgment

•Visual preception