What is mixed dementia?

Mixed dementia is when brain changes from more than one cause of dementia occur at the same time. The Alzheimer's Association says the most common form combines the abnormal protein deposits of Alzheimer's disease with the blood vessel problems of vascular dementia. Alzheimer's changes also often coexist with Lewy bodies, and some people have all three. It is infrequently diagnosed during life.

Mixed dementia is most often a combination of Alzheimer's disease and vascular dementia. The Alzheimer's Association says Alzheimer's brain changes also frequently occur with Lewy bodies, the hallmark of dementia with Lewy bodies, and some people have changes linked to all three conditions. In one NIA-funded study, previously undetected blood vessel disease was the most common coexisting change, and Lewy bodies the second most common.

It appears more common than diagnoses suggest. The Alzheimer's Association reports that in an NIA-funded study comparing diagnoses made during life with brain autopsies, 54% of people diagnosed with Alzheimer's also had other dementia-related brain changes. Most people with mixed dementia are diagnosed with a single type during life, most often Alzheimer's, partly because most of these brain changes cannot yet be measured in living people.

Mixed dementia symptoms vary with the types of brain changes involved and the brain regions affected. The Alzheimer's Association says that in many cases they are similar to, or impossible to tell apart from, those of Alzheimer's or another single type of dementia, while in other cases they suggest more than one type is present. Long-term studies are still clarifying how symptoms relate to the underlying changes.

It may be. The Alzheimer's Association says many researchers believe a combination of two or more types of dementia-related brain changes may have a greater impact on the brain than one type alone, and evidence suggests having more than one may raise the chance a person develops symptoms. No drug is FDA approved specifically for mixed dementia, so doctors usually base treatment on the diagnosed type.