dementia can have many causes many of which are unknown. also there are different kinds of dementia it's not just one condition. sometimes dementia can have a cause like lead poisoning or mercury poisoning other heavy metals certain poisons etc. sometimes it just happens and the cause is never found. sometimes it can happen with aging. a person's life expectancy doesn't really change if they have dementia which is the really heartbreaking part - if their body is maintained even after they cannot think anymore they may live on. you will find more information by checking wikipedia under this same topic mayoclinic. com or by reading here. <link>
what are causes of dementia and how long o you live once you have it? . school project