Mixed Dementia

Mixed dementia is a condition where brain changes from more than one type of dementia occur at the same time. The most common form combines Alzheimer’s disease and vascular dementia, though other combinations are also possible.

Table of contents

• What is mixed dementia?
• How common is mixed dementia?
• Causes and risk factors
• Signs and symptoms
• Diagnosis
• Treatment
• Stages of mixed dementia
• Outlook and prognosis

What is mixed dementia?

Mixed dementia is a condition in which abnormalities from more than one type of dementia are present in the brain simultaneously^[2]. In other words, a person has brain changes linked to at least two different forms of dementia at the same time.

In the most common form of mixed dementia, the abnormal protein deposits associated with Alzheimer’s disease coexist with blood vessel problems linked to vascular dementia^[2]. Brain changes from Alzheimer’s disease also often occur alongside Lewy bodies, which are abnormal deposits of a protein called alpha-synuclein inside nerve cells^[2].

In some cases, a person may have brain changes linked to all three conditions—Alzheimer’s disease, vascular dementia, and dementia with Lewy bodies^[2]. Other combinations can also occur, including Alzheimer’s disease with frontotemporal dementia or Parkinson’s disease dementia^[4].

How common is mixed dementia?

Researchers don’t know exactly how many older adults currently diagnosed with a specific type of dementia actually have mixed dementia, but studies of brain tissue after death indicate that the condition may be significantly more common than previously realized^[2].

Studies of the brain after death play a key role in understanding mixed dementia because scientists can’t yet measure most dementia-related brain changes in living individuals. In these studies, researchers compare each person’s cognitive health and any diagnosed problems during life with analysis of the brain after death^[2].

Data from research studies show that more than 50 percent of those whose brains met criteria for dementia had evidence of more than one type of brain change^[2]. Brain autopsy studies suggest that most older adults over the age of 80 with dementia have some form of mixed dementia^[5]. One review noted that about 22% of elderly people with dementia have mixed dementia based on examination of brain tissue^[8].

Causes and risk factors

Doctors are still learning what causes mixed dementia^[4]. Evidence suggests that having more than one type of brain change from dementia may increase the risk. It’s possible that mixed dementia is related to vascular conditions, because most cases involve vascular dementia^[4]. Some experts think it may be linked to low blood flow to the brain combined with other risk factors^[4].

Most people develop mixed dementia when they are older. It may happen when a person is 50 years old or later, but it’s most common in those older than 75^[4]. Mixed dementia occurs in all racial and ethnic groups, though it appears to be more common in men^[4].

The main risk factors for mixed dementia include^[4]:

• Being older
• Blood vessel damage in the brain
• High blood pressure

For the most common form—Alzheimer’s disease combined with vascular dementia—increasing age and vascular conditions that affect blood vessels, such as high blood pressure, are the main risk factors^[5].

Since mixed dementia involves many different conditions, risk factors related to each type can trigger the onset and progression of the disease^[18]. For Alzheimer’s disease, important factors include age, family history, and heredity. Having a parent or sibling with Alzheimer’s disease increases the likelihood of developing the illness^[18]. A specific gene variant called APOE-e4 is an important risk gene, though inheriting this gene doesn’t guarantee that a person will develop Alzheimer’s disease^[18].

Major risk factors for vascular dementia include history of heart attack or stroke, atherosclerosis (buildup of fats and other substances in artery walls), high cholesterol, diabetes, smoking, obesity, and atrial fibrillation (irregular heartbeat)^[18].

Signs and symptoms

Mixed dementia symptoms may vary depending on the types of brain changes present and the regions of the brain affected^[2]. Because several factors are involved, researchers are unable to clearly identify symptoms that are unique to mixed dementia^[22].

A person with mixed dementia may show symptoms of Alzheimer’s disease, vascular disease, Lewy body dementia, frontotemporal dementia, Parkinson’s disease, or another type of dementia^[4]. In some cases, the symptoms may be difficult to distinguish from one another^[4].

The most prominent symptoms often include problems with thinking, walking, and performing everyday activities^[5]. Many people with mixed dementia also experience^[5]:

• Depression, which can result in less motivation to perform usual activities or a lack of interest in the world around them
• Extreme anxiety about daily life, which may show as asking questions repeatedly, preparing for appointments well ahead of time, and using notes and reminders constantly
• Lack of initiative about tasks that used to be routine, though now feel overwhelming
• Frequent agitation as people become less able to interpret their environment and control or express their feelings

Studies suggest that the presence of two or more dementia conditions may cause a greater impact on the brain and speed up the progression of symptoms compared to having just one type^[22].

Diagnosis

Diagnosing mixed dementia is challenging. One major problem experts face is that they cannot measure most dementia-related brain changes in people who are alive^[22]. The difficulty in identifying clear symptoms makes it hard for doctors to diagnose combination dementia^[22].

Getting an accurate diagnosis of mixed dementia is difficult, and most cases are identified and diagnosed based on examination of brain tissue after death^[5]. Because dementia symptoms vary widely between different types, it can be hard to distinguish between them^[5].

During diagnosis, a healthcare professional reviews medical history and symptoms and conducts a physical exam^[14]. A person close to the patient may be asked about symptoms as well. No single test can diagnose dementia, and several tests may be needed to help pinpoint the problem^[14].

Tests that may be used include^[14]:

• Cognitive and thinking tests that evaluate memory, orientation, reasoning and judgment, language skills, and attention
• Examination of movement, balance, senses, reflexes, and other areas
• Brain scans such as CT (computed tomography) or MRI (magnetic resonance imaging) to check for stroke, bleeding, tumor, or fluid buildup
• PET scans (positron emission tomography) that can show patterns of brain activity and determine whether specific proteins associated with Alzheimer’s disease have been deposited in the brain
• Blood tests to look for changes that affect brain function, such as low vitamin B-12 or thyroid problems
• Sometimes examination of spinal fluid for infection, inflammation, or markers of disease

Researchers are working on gaining a greater understanding of the connection between brain changes and decline in cognitive functions in those affected by mixed dementia^[22].

Treatment

There is no cure currently available for mixed dementia, and no treatment approved by the US Food and Drug Administration specifically for this condition^[5][22]. Treatment approaches focus on managing symptoms and trying to prevent further damage to the brain.

Treatment options are usually based on the types of dementia that have been diagnosed^[22]. For example, a doctor may prescribe medication to treat symptoms of Alzheimer’s disease if the symptoms match that disease. Physicians may also prescribe medication to treat heart or blood vessel diseases as a way of controlling vascular changes that affect the brain^[22].

The main aim of treatment for vascular dementia—a common component of mixed dementia—is to treat the underlying cause to help stop the condition from getting worse^[13]. This usually involves making healthy lifestyle changes, such as^[13]:

• Eating a healthy, balanced diet, including following a low-salt diet to manage high blood pressure
• Losing weight if overweight
• Stopping smoking
• Getting fit through regular physical activity
• Cutting down on alcohol

Medicines may also be offered to treat underlying causes and help stop mixed dementia from getting worse. These include^[13]:

• Medicines to treat high blood pressure
• Medicines to treat high cholesterol, such as statins
• Medicines such as low-dose aspirin or clopidogrel to reduce the risk of blood clots and further strokes
• Blood-thinning medicines, such as warfarin, which can also reduce the risk of blood clots and further strokes
• Medicines to treat diabetes

Controlling vascular risk factors is particularly important. While there is no current treatment to reverse the effects of vascular damage, preventing additional vascular damage—particularly stroke—can be an effective way to lower someone’s risk of worsening dementia^[27]. People with mixed dementia should have their blood pressure checked and blood fat levels measured at least once a year^[27].

Several therapies and practical measures can help make everyday living easier. These include^[13]:

• Occupational therapy to identify problems in everyday life and find practical solutions
• Speech and language therapy to help improve communication problems
• Physiotherapy (physical therapy) to help with movement difficulties
• Psychological therapies, such as activities and exercises to improve memory, problem-solving, and language
• Relaxation techniques, such as massage, music, or dance therapy
• Social interaction and leisure activities
• Making changes to the home, such as removing loose carpet and potential trip hazards, ensuring good lighting, and adding grab bars and handrails

Stages of mixed dementia

Just like other forms of dementia, mixed dementia is a disease that gets worse over time^[4]. There are seven stages^[4]:

1. Normal functioning. When mixed dementia first starts to develop, there may be no signs or symptoms of dementia at all. The way the brain works may be normal.
2. Very mild cognitive decline. In the second stage, there may be small lapses in memory. A person may forget things here and there, which may seem like a normal part of aging.
3. Mild cognitive decline. During stage three, early signs of dementia may appear. A person may have trouble remembering things and finding words to describe something.
4. Moderate cognitive decline. Memory loss may become more noticeable. It may start to get in the way of daily tasks like keeping up with bills and making plans.
5. Moderately severe cognitive decline. Day-to-day functioning may become a struggle. A person may need help with self-care tasks like taking a shower and getting dressed.
6. Severe cognitive decline. A person may need a lot of help with things they do every day. It may be hard to communicate with others.
7. Very severe cognitive decline. A person may no longer be able to do basic functions like walking and talking. At this point, full-time, around-the-clock care may be needed.

Outlook and prognosis

The outlook for people with mixed dementia varies depending on the specific types of dementia present and individual factors. Research suggests that having multiple types of dementia-related brain changes may have a greater impact on brain function and may speed up the progression of symptoms compared to having just one type of dementia^[22].

While there is currently no cure for mixed dementia, steps can be taken to help slow its progression. The main approach is to treat underlying causes—particularly vascular conditions—to help prevent further damage to the brain^[13]. If vascular risk factors are not properly managed, recurring strokes and worsening dementia symptoms may occur^[27].

It’s important for people with mixed dementia and their caregivers to get support from healthcare professionals and support groups. Organizations such as the Alzheimer’s Society and Dementia UK can provide helpful information and support^[13].