What Is Mixed Dementia?
What Is Mixed Dementia?
It is common for people to have mixed dementia—a combination of two or more disorders, at least one of which is dementia. A number of combinations are possible. For example, some people have both Alzheimer’s disease and vascular dementia.
Some studies indicate that mixed dementia is the most common cause of dementia in the elderly. For example, autopsy studies looking at the brains of people who had dementia indicate that most people age 80 and older had mixed dementia—a combination of brain changes related to Alzheimer’s disease (amyloid and tau), cerebrovascular disease (such as stroke), and, in some instances, Lewy body dementia (Lewy bodies). These studies suggest that mixed dementia is caused by both Alzheimer’s-related neurodegenerative processes and vascular disease-related processes.
In a person with mixed dementia, it may not be clear exactly how many of a person’s symptoms are due to Alzheimer’s or another type of dementia. In one study, approximately 40 percent of people who were thought to have Alzheimer’s were found after autopsy to also have some form of cerebrovascular disease. In addition, several studies have found that many of the major risk factors for vascular disease also may be risk factors for Alzheimer’s disease.
Researchers are still working to understand how underlying disease processes in mixed dementia influence each other. It is not clear, for example, if symptoms are likely to be worse when a person has brain changes reflecting multiple types of dementia. Nor do we know if a person with multiple dementias can benefit from treating one type, for example, when a person with Alzheimer’s controls high blood pressure and other vascular disease risk factors.
