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Mixed dementia is a combination of more than one form of dementia. When there is more than one form of dementia present, care is complicated but there are changes that make a difference.

About one out of every 10 people who has a major neurocognitive disorder is diagnosed with mixed dementia. This condition is a combination of the disease processes of two different forms of dementia. Doctors also refer to this state as multifactorial dementia. Most common in people who are over 75, mixed dementia requires some changes from usual standards of care to maximize the qualify of life and longevity of the patient.

Common symptoms of mixed dementia

The most common form of mixed dementia is Alzheimer's disease with vascular dementia. Alzheimer's disease is accompanied by accumulation of tangled proteins that "strangle" neurons, primarily in the back of the brain. Vascular dementia is a complication of high blood pressure and bad cholesterol that causes transient ischemic attacks (mini-strokes) that damage vessels that carry blood to the front of the brain.

Mixed dementia presents the symptoms of both Alzheimer's and vascular dementia. Alzheimer's causes memory problems, loss of language, and confusion. Vascular dementia causes attention deficits, difficulty planning, and sluggish thinking. One set of symptoms may predominate at first, but all of them can occur at the same time.

Another relatively common form of mixed dementia is Alzheimer's disease with Lewy body dementia. Lewy bodies are abnormal proteins that form inside neurons. These changes produce symptoms similar to Parkinson's, while Alzheimer's follows a predictable progression of symptoms and disability. Lewy body dementia adds visual hallucinations and very disturbed sleep to the usual symptoms of Alzheimer's. Symptoms may fluctuate greatly from day to day in this combination of dementias.

A few people who have dementia have all three forms of dementia at the same time. It may be that the various forms of dementia develop at different ages, so only older people (in their mid-seventies and up) develop more than one form of the disease.

The diagnostic dilemma in mixed dementia

How common is mixed dementia? Researchers don't really know, because precise diagnosis requires taking a sample of tissue from the brain of the person who has the disease. In a study involving autopsies of patients who willed their brains for study after death, however, 54 percent of people who had been diagnosed with Alzheimer's were found also to have brain changes from other forms of dementia, usually vascular dementia or Lewy body disease.

People who develop mixed dementia tend to have greater problems with "executive function," making decisions and carrying them out, than people who have Alzheimer's disease. However, Alzheimer's patients tend to suffer greater memory loss.

Treatments for mixed dementia

There is no cure for any kind of dementia. Some people do better longer, however, with good care and appropriate medications. So does a diagnosis of mixed dementia make any difference in care? It turns out that knowing that dementia is "mixed" can lead to appropriate steps to slow down the progression of the disease and increase quality of life.

  • When there is vascular dementia, it is critically important to avoid new transient ischemic attacks and new vascular damage in the brain. That requires careful attention to managing cholesterol, keeping blood pressure within healthy limits, and using anticoagulant medications correctly to prevent new blood clots. These are not tasks dementia patients can achieve on their own. Healthy LDL and HDL levels are determined with reference to the presence or absence of diabetes. Studies show reduction in the rate of progression of vascular dementia when systolic blood pressure is kept below 130 mg/dl. Aspirin can be helpful in preventing Alzheimer's, but usually aspirin plus an anticoagulant (for example, clopidogrel, marketed as Plavix) is needed to see measurable, positive changes.
  • Along with managing cholesterol, it is important to keep homocysteine levels normal. Homocysteine in excess produces hot spots of inflammation in the brain. To keep homocysteine down, it is necessary to get vitamins B6, B12, and folate. And to get B12, sometimes it is necessary to give the vitamin by injection, particularly in people who have digestive problems.
  • In diabetic patients, good blood sugar regulation is critical. That means avoiding both chronically high blood sugar levels (the guideline is keeping HbA1C under 7.0 percent, although many diabetics have trouble meeting that goal) and especially avoiding hypoglycemia, blood sugar levels that fall so low as to cause loss of consciousness. Diabetes can cause "thinning" of the frontal cortex that precedes vascular dementia by up to 10 years. Blood sugar control today can prevent dementia progression years from now.
  • Two studies show that diets providing vegetables, fruits, nuts, soy proteins, grains and fish slow the progression of Alzheimer's disease. Good diet won't reverse Alzheimer's, but it may slow it down.
  • One study shows that getting at least 30 minutes of exercise at least three times a week slows the progression of both Alzheimer's disease and vascular dementia. It improves independence and makes daily activities easier. 
Good risk management and good health habits make a difference over the course of years of the disease. None of these recommendations will make a different in managing mixed dementia over the short term, but there is good scientific evidence they are useful for long-term optimization of quality of life.

  • Bogolepova AN. [A modern concept of mixed dementia]. Zh Nevrol Psikhiatr Im S S Korsakova. 2015.115(5):120-126. doi: 10.17116/jnevro201511551120-126. Review. Russian.PMID: 26356171.
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  • Zekry D, Hauw JJ, Gold G. Mixed dementia: epidemiology, diagnosis, and treatment. J Am Geriatr Soc. 2002 Aug.50(8):1431-8. Review. PMID: 12165002.
  • Photo courtesy of SteadyHealth

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