It is common for people with dementia to have mixed dementia—a combination of two or more types of 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 probably had mixed dementia caused by a combination of brain changes related to Alzheimer's disease, vascular disease-related processes, or another neurodegenerative condition. Some studies suggest that mixed vascular-degenerative dementia is the most common cause of dementia in older adults.
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 disease. In one study, researchers who examined older adults' brains after death found that 78 percent had two or more pathologies (disease characteristics in the brain) related to neurodegeneration or vascular damage. Alzheimer's was the most common pathology but rarely occurred alone.
Researchers are trying to better understand how underlying disease processes in mixed dementia influence each other. In the study described above, the researchers found that the degree to which Alzheimer's pathology contributed to cognitive decline varied greatly from person to person. In other words, the impact of any given brain pathology differed dramatically depending on which other pathologies were present.
For More Information About Mixed Dementia
NIA Alzheimer’s and related Dementias Education and Referral (ADEAR) Center
The National Institute on Aging’s ADEAR Center offers information and free print publications about Alzheimer’s disease and related dementias for families, caregivers, and health professionals. ADEAR Center staff answer telephone, email, and written requests and make referrals to local and national resources.