Alzheimer’s disease is the most common form of dementia, affecting up to 70% of all people with dementia
- Alzheimer's disease damages the brain, resulting in impaired memory, thinking and behaviour
- The biggest risk factor for having Alzheimer’s disease is increasing age, with three in ten people over 85 having dementia
- Sporadic Alzheimer’s disease can affect anyone of any age
- Familial Alzheimer’s disease is a very rare genetic condition, with an age of onset of less than 65 years
What is Alzheimer's disease?
Alzheimer’s disease is the most common form of dementia, affecting up to 70% of all people with dementia. It was first recorded in 1907 by Dr Alois Alzheimer. Dr Alzheimer reported the case of Auguste Deter, a middle-aged woman with dementia and specific changes in her brain. For the next 60 years Alzheimer’s disease was considered a rare condition that affected people under the age of 65. It was not until the 1970s that Dr Robert Katzman declared (rather boldly at the time) that "senile dementia" and Alzheimer’s disease were the same condition and that neither were a normal part of aging.
Alzheimer’s disease can be either sporadic or familial.
Sporadic Alzheimer's disease can affect adults at any age, but usually occurs after age 65 and is the most common form of Alzheimer's disease.
Familial Alzheimer’s disease is a very rare genetic condition, caused by a mutation in one of several genes. The presence of mutated genes means that the person will eventually develop Alzheimer's disease, usually in their 40's or 50's.
The Healthy Human Brain
The whole brain is fed and provided with oxygen by a complex network of arteries, veins and capillaries. This vascular network is strictly controlled and segregates the brain from the rest of the blood stream. The blood brain barrier protects the brain from infection, but consequently if the brain does become infected it is difficult to treat, as many antibiotics are too large in their molecular structure to cross the barrier. This is also a major problem when finding agents to treat Alzheimer’s disease, as they must pass this barrier to target the brain.
Behind the ears and temples are the temporal lobes of the brain. These regions process speech and working memory, and also ‘higher’ emotions such as empathy, morality and regret. Beneath the forebrain are the more primitive brain regions such as the limbic system. The limbic system is a structure that is common to all mammals and processes our desires and many emotions. Also in the limbic system is the hippocampus – a region that is vital for forming new memories.
The cerebellum is at the back of the brain, which stores our muscle memory so we can do things without thinking - such as riding a bike. The midbrain and brain stem are the most primitive regions of the brain. They control bodily functions such as heart rate and digestion and act as an interface between the spinal cord and the rest of the brain.
All these complex tasks are mediated by the connections between the brain cells (neurons) called synapses. In the adult human brain there are around 100 billion brain cells, each connected to its neighbours by 5-10,000 synapses.
Our brains form a million new connections – a million new synapses – every second we are alive. The pattern and strength of the connections is constantly changing and no two brains are alike.
It is in these changing connections that memories are stored, habits learned and personalities shaped, by reinforcing certain patterns of brain activity, and losing others.
Brain cells communicate though synapses in a variety of ways. Signals pass move across the synapse in the form of chemicals that are known as neurotransmitters. Neurotransmitters a passed from one brain cell, across the synapse (connection) and to the receiving brain cell, which collects the neurotransmitter with a receptor. The receiving cell can then send out another burst of neurotransmitters to other brain cells to pass the message on.
The Brain with Alzheimer’s Disease
Going back to the 1900s, Dr Alzheimer examined the brain of his patient, Mrs Deter, upon her death. He found shrinking of the outer layer of the brain or cortex – the region of the brain involved in memory, language and judgment. We know that the so called shrinking of the brain is caused by the death of the brain cells.
Dr Alzheimer also found two types of deposits in Deter’s brain. One kind was found outside the brain cells, which are known plaques and the other type of deposit was found inside brain cells known as “neurofibrillary tangles. These plaques impair synapses so signals cannot pass between brain cells. Tangles kill brain cells by preventing the normal transport of food and energy around the brain cell.
As brain cells die the brain shrinks, which can be detected using imaging such as magnetic resonance imaging (MRI).
The outer part of the brain is usually the area affected first by the disease. Short-term memory loss is therefore one of the first symptoms of Alzheimer’s disease. But as the disease progresses to deeper parts of the brain, long-term memory is also lost. The disease also affects many of the brain's other functions and consequently, many other aspects of behaviour are disturbed.
Apart from the few individuals with Familial Alzheimer's disease, it is not known why one individual gets Alzheimer's disease late in life and another does not. Scientists are investigating what triggers the formation of plaques and tangles and about other chemical changes that damage brain cells in Alzheimer's disease.
A variety of suspected causes are being investigated including factors in the environment, biochemical disturbances and immune processes. The cause may vary from person to person and may be due to one factor or a number of factors.
Symptoms of Alzheimer's disease
In the early stages the symptoms of Alzheimer's disease can be very subtle. However, it often begins with lapses in memory and difficulty in finding the right words for everyday objects.
Other symptoms may include:
- Persistent and frequent memory difficulties, especially of recent events
- Vagueness in everyday conversation
- Apparent loss of enthusiasm for previously enjoyed activities
- Taking longer to do routine tasks
- Forgetting well-known people or places
- Inability to process questions and instructions
- Deterioration of social skills
- Emotional unpredictability
Symptoms vary and the disease progresses at a different pace according to the individual and the areas of the brain affected. A person's abilities may fluctuate from day to day, or even within the one day, becoming worse in times of stress, fatigue or ill-health.
How does Alzheimer's disease progress?
The rate of progression of the disease varies from person to person.
However, the disease does lead eventually to complete dependence and finally death, usually from another illness such as pneumonia. A person may live from three to twenty years with Alzheimer's disease, with the average being seven to ten years.
How is Alzheimer's disease diagnosed?
There is currently no single test to identify Alzheimer's disease. The diagnosis is made only after careful clinical consultation.
The clinical diagnosis might include:
- A detailed medical history
- A thorough physical and neurological examination
- A test of intellectual function
- Psychiatric assessment
- A neuropsychological tests
- Blood and urine tests
- Lumbar puncture for cerebral spinal fluid tests
- Medical imaging (MRI, PET)
These tests will help to eliminate other conditions with similar symptoms such as nutritional deficiencies or depression. After eliminating other causes, a clinical diagnosis of Alzheimer's disease can be made with about 80% to 90% accuracy if the symptoms and signs are appropriate. The diagnosis can only be confirmed after death by examination of the brain tissue.
It is important to have an early and accurate diagnosis to determine whether a treatable condition other than Alzheimer's disease, is causing the symptoms. If Alzheimer's disease is diagnosed, medical treatment and other assistance can be discussed.
Is there treatment available?
At present there is no cure for Alzheimer's disease. However, one group of drugs called cholinergeric drugs appears to be providing some temporary improvement in cognitive functioning for some people with mild to moderate Alzheimer's disease.
Drugs can also be prescribed for secondary symptoms such as restlessness or depression or to help the person with dementia sleep better.
Community support is available for the person with Alzheimer's disease, their families and carers. This support can make a positive difference to managing dementia. Alzheimer's Australia provides support, information and counselling for people affected by dementia. Alzheimer's Australia also aims to provide up-to-date information about drug treatments.
For more information contact the National Dementia Helpline on 1800 100 500.
For a range of books and videos contact our Library.
For advice, common sense approaches and practical strategies on the issues most commonly raised about dementia, read our Help Sheets.