Mixed dementia: What is it, and how does it progress?
Dementia is a progressive decline of mental abilities, including memory loss, personality changes, difficulty processing thoughts and speech and language problems. When 2 or more diseases cause the symptoms, this is called mixed dementia, or multifactorial dementia.
Dementia is not just a normal part of aging. Although symptoms are barely noticeable in the beginning, they increase in severity over the years. Some types of dementia are reversible, such as those caused by depression, medication side effects, vitamin or mineral deficiencies, thyroid problems or trauma to the head.
In this article, we’ll take a look at the most common types of mixed dementia, how the condition progresses, and how you can lower your risk.
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Mixed dementia pathophysiology
Most people with dementia are only diagnosed with one type. However, many may have more than one disease which is causing their symptoms. (4)
The combination of Alzheimer’s and vascular dementia is the most common form of mixed dementia; Alzheimer’s with Lewy body disease is also thought to be common. (5)
Because mixed dementia has more than one cause, it can be difficult to diagnose and identify which symptoms are related to each disease. (6)
First, it is important to understand the different types of dementia and how the symptoms differ.
How many types of dementia are there?
Although there are lots of conditions which cause dementia, here we will focus on the four main types.
1. Alzheimer’s Disease
Alzheimer’s may be the main cause of dementia in as many as 60-80% of cases. (7)
Abnormal structures called “plaques” and “tangles” build up in the brains of people with Alzheimer’s. Because of these structures, connections between nerve cells are lost, which causes nerve cells to die, leading to lost brain tissue.
Alzheimer’s is a progressive disease and the main symptoms are memory loss, confusion, disorientation, and later, personality changes. (8)
Cholinesterase inhibitors are prescribed for mild to moderate Alzheimer’s disease. These drugs may help reduce some symptoms. Memantine can improve functioning in later stages. (9)
Other treatments for Alzheimer’s include anti-anxiety drugs, anticonvulsants, and in severe cases, antipsychotics.
2. Vascular Dementia
The 2nd most common type of dementia, vascular dementia, is caused by reduced blood supply to the brain due to damaged blood vessels.
Brain cells need a constant supply of blood to bring oxygen and nutrients, and the blood is delivered to the brain through a network of vessels called the vascular system. When this system becomes damaged in the brain, blood vessels can leak or become blocked.
If brain cells are cut off from blood supply, they die. This results in problems with memory, thinking and reasoning.
Vascular dementia can be caused by a stroke that blocks an artery in the brain, or by damaged blood vessels in the brain resulting from high blood pressure, diabetes or brain hemorrhage. Symptoms may develop in “steps”, where noticeable changes occur suddenly, followed by periods of stability. (10)
Treatment for vascular dementia is focussed on lowering blood pressure and risk of vascular damage. You can limit your risk of vascular damage by reducing your cholesterol, keeping arteries clear and controlling your blood sugar if you have diabetes.
3. Dementia with Lewy bodies
Lewy bodies are protein deposits that appear in nerve cells in the brain. These deposits affect chemicals in the brain which in turn can lead to problems with movement, thinking, behavior, and mood.
The symptoms of dementia with Lewy bodies (DLB) have some characteristics that differ from Alzheimer’s. Patients with DLB may have visual hallucinations, REM sleep disorder, and difficulty in spatial perception and movement in the early stages of the disease. DLB does not always cause memory loss until later on. (11)
Lewy bodies are also present in Parkinson’s disease, and people with DLB may develop some motor symptoms of Parkinson’s as the disease progresses. (12)
Cholinesterase inhibitors that are used for Alzheimer’s are also used to treat DLB, as well as antidepressants, and clonazepam for REM sleep disorder. (13)
4. Frontotemporal Dementia
This is a less common type of dementia, however it is more often diagnosed in younger patients in the 45-65 age range. It is sometimes referred to as Pick’s disease.(14)
In this type of dementia, the most prominent early symptoms are behavior and personality change. Memory loss tends to occur later on. Other symptoms can be related to movement and difficulties with speech.
It is caused by clumps of abnormal protein that gather in brain cells. (15)
Antidepressants and antipsychotics may help with some symptoms, however medicines that help to slow the decline of Alzheimer’s do not work for frontotemporal dementia. (16)
The most common types of mixed dementia
1. Alzheimer’s and Vascular Dementia
The term mixed dementia is most often used to refer to the combination of Alzheimer’s (AD) and vascular dementia (VaD). However, it is challenging to accurately diagnose mixed dementia. (17)
They are often treated as separate diseases, though some evidence suggests that the brain lesions caused by AD and VaD often occur together, and the interaction of these brain lesions may increase the severity of cognitive decline.
Some evidence suggests that VaD, and perhaps also mixed dementia are preventable if vascular risk factors are controlled and strokes are prevented. (18)
2. Alzheimer’s and Lewy Body Disease
Lewy bodies may be present in up to 50% of Alzheimer’s cases. (18)
Imaging tests cannot confirm the presence of Lewy bodies, so this type of dementia is hard to diagnose when combined with AD.
However, the mix of Alzheimer’s and Lewy bodies is concerning because some of the treatments prescribed for Alzheimer’s, such as antipsychotic medicines, can be dangerous to people with Lewy body disease. (19)
How does mixed dementia progress?
The impact of one type of dementia varies depending on the other diseases that are present. Each type of dementia progresses slightly differently, and also varies from person to person.
Generally, dementia progresses in stages. The following is a guide to how mixed dementia, with Alzheimer’s as the primary cause, can progress.
Mild cognitive impairment
Mild cognitive impairment, or MCI, may affect as many as 20% of people over the age of 65. (20)
Signs of MCI are a decline in short term memory and thought processes. People with MCI might forget appointments or find it difficult to complete a challenging task.
Not everyone with MCI will go on to develop dementia, but around 60-65% will. Lifestyle changes at the onset of MCI that may help to prevent or slow down the onset of dementia. (21)
To minimize the risk of MCI progressing to dementia, the Alzheimer’s Association recommends regular exercise, quitting smoking, maintaining a healthy diet, and regular mental and social stimulation. (22)
People in the early stages of dementia can usually live independently, however they will begin to notice that the symptoms disrupt their daily life.
Common symptoms of early-stage dementia are memory lapses, forgetting recent events, getting lost in familiar places. There may also be some personality changes, such as becoming more withdrawn or depressed, and patients may struggle to organize and express their thoughts.
People in the middle stage need some assistance in their lives. They will likely experience increased confusion, poor judgement, loss of more memories. Keeping up with daily tasks and personal hygiene becomes more challenging.
They may also experience personality and behaviour changes like restlessness, agitation and paranoia.
The later stages are characterised by further cognitive decline and reduction of physical capabilities. Some people may be unable to communicate or be limited to just a few words a day. They will need full-time assistance with simple tasks like eating and getting dressed.
They may be unable to walk or sit up, and eventually lose control of the bladder and bowels and struggle to swallow.
This can be a highly distressing time for patients and caregivers. The patient will be highly vulnerable to infections and the priority for doctors is to provide palliative care and pain relief. (23)
What is the life expectancy for someone with mixed dementia?
A 2015 survey from the Office for National Statistics found that dementia was the leading cause of death in England. (24)
The average life expectancy after diagnosis of Alzheimer’s is between 3 and 11 years, however some survive 20 years or more. (25)
Symptoms like forgetfulness, confusion and communication problems are caused by damage to brain cells. But, because the brain controls the whole body, this damage and death of brain cells eventually causes multiple organ failure.
When dementia results from more than one cause, this means that the effects may be compounded. For example, the life expectancy of vascular dementia is shorter than that of Alzheimer’s. This is due in part to the other risks associated with vascular issues such as stroke and heart attack.
In all cases, early diagnosis is crucial to lengthening life expectancy and quality of life.
How can you lower your risk of dementia?
- Research suggests that exercise is key to preventing and slowing the progression of dementia (26)
- Getting plenty of sleep is vital for a healthy brain. Sleep deprivation may encourage the build-up of proteins associated with Alzheimer’s. (27)
- Keeping diabetes at bay can help reduce your risk of Alzheimer’s. (28)
- Reduce stress. Some studies show that stress can lead to cognitive decline. (29)
- Keep your mind active. Brain training, puzzles, and games can help sharpen your cognitive function. (30)
Mixed dementia is harder to diagnose and treat because there are different diseases causing the decline of mental abilities.
Alzheimer’s is the most prevalent cause of dementia. Vascular dementia and dementia with Lewy bodies are two other common diseases that can be present with Alzheimer’s.
As yet, there is no cure for dementia, but early diagnosis and treatment can help slow the rate of progression.
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