Mixed Dementia

Mixed dementia is when a person has more than one type of dementia at the same time. The most common combination is Alzheimer's disease with vascular dementia. There is no cure, but medicines, therapies and support can help manage symptoms.

How common is it?

Mixed dementia accounts for at least 1 in 10 dementia diagnoses, according to Alzheimer's Society and Dementia UK, and is most common in people over 75.

The true figure may be much higher, because it often goes unrecognised during life. In one US study funded by the National Institute on Aging, 94% of participants diagnosed with dementia had been diagnosed with Alzheimer's disease. Autopsies showed that 54% of them also had other brain changes, most often blood vessel disease and then Lewy bodies.

Types of mixed dementia

The most common combinations are:

• Alzheimer's disease and vascular dementia: the most common form
• Alzheimer's disease and Lewy body dementia: the symptoms of both overlap
• All three together: some people have changes linked to Alzheimer's, vascular disease and Lewy bodies

Other types of dementia can be involved, but this is less common.

Symptoms

There is no fixed set of symptoms. They depend on which types of dementia are present, how much each contributes, and which parts of the brain are affected. Often one type causes more symptoms than the other.

Symptoms can be typical of each type:

Other possible symptoms include communication difficulties and changes in personality, behaviour and mood.

Sometimes the symptoms look just like Alzheimer's or another single type. This can make mixed dementia hard to spot. A review of the evidence found that people with mixed Alzheimer's and vascular dementia tend to do worse than people with Alzheimer's alone on tests of attention, memory, naming and planning.

Causes

Mixed dementia happens when the brain changes of more than one type of dementia occur together. In the most common form, these are the protein deposits of Alzheimer's disease and the blood vessel problems of vascular dementia. Having more than one type of change may affect the brain more than one alone, and may make symptoms more likely.

How it is diagnosed

Mixed dementia is difficult to diagnose because symptoms overlap, and it is hard to see every type of disease in a living brain. A person may be diagnosed with only one type, or the wrong type. Doctors usually base the diagnosis on the main disease they think is causing symptoms, and diagnose mixed dementia when someone clearly shows signs of at least two types.

There are no agreed criteria for diagnosing mixed Alzheimer's and vascular dementia. Brain scans can support the diagnosis but can't confirm it on their own.

The first step is usually a visit to a GP, who can refer you for further assessment, often at a memory clinic. If you're concerned that a diagnosis doesn't fit all of the symptoms, it's reasonable to raise this with your specialist. Getting the diagnosis right matters because it can affect which treatments are suitable.

Treatment

There is no cure and no treatment that stops mixed dementia progressing. No medicine has been approved in the US specifically for it, so doctors generally prescribe according to the type or types they think are involved.

Medicines

• Alzheimer's medicines: donepezil, rivastigmine or galantamine may be prescribed in the early to middle stages if Alzheimer's is thought to be involved. Memantine may be prescribed if donepezil can't be taken, or added as symptoms progress.
• Medicines for vascular risk: people with vascular dementia may take medicines for high blood pressure, high cholesterol or type 2 diabetes, or after a stroke. Managing these risks may help protect the brain from further vascular changes, though a review of the evidence found no proof that it changes how dementia progresses.

These medicines aren't suitable for everyone. For example, Alzheimer's medicines may make symptoms worse if frontotemporal dementia is also present. Alzheimer's Society notes that no medicine has been shown to improve symptoms of vascular dementia itself, and trials in mixed dementia show only mild benefits for thinking and memory.

Therapies and support

Options that may help include occupational therapy, talking therapies, cognitive stimulation and rehabilitation, reminiscence and life story work, and music or art therapy. Physiotherapy may help with movement problems when Lewy body disease is involved.

Lifestyle

A balanced diet, exercise suited to the person's abilities, keeping to a healthy weight, staying within 14 units of alcohol a week and stopping smoking are all recommended. A healthy diet and regular exercise have been linked to slower progression of symptoms.

How it progresses

It is very hard to predict how quickly mixed dementia will progress. It depends on age, the types involved, treatment and lifestyle. Like other dementias, it is often described in early, middle and late stages, and you can read more on our stages of dementia page.

Having two types can make symptoms more noticeable, and Dementia UK says mixed dementia can progress faster overall than a single type.

Life expectancy

None of the sources we reviewed give a life expectancy figure specific to mixed dementia. Our page on dementia life expectancy covers what is known for each main type.

Getting help

If you notice memory, thinking or behaviour changes in yourself or someone else, see a GP. In the UK, Dementia UK runs a dementia helpline. In the US, the Alzheimer's Association publishes information on mixed dementia. Our page on the difference between dementia and Alzheimer's may also help.