A progressive neurological condition
Alzheimer’s disease is the most common cause of dementia, affecting memory, thinking, behaviour and daily function. It is associated with changes in the brain, including the formation and clumping of abnormal proteins.
What is Alzheimer’s disease?
Alzheimer’s disease is the leading cause of dementia worldwide. It is a brain disorder that gradually causes loss of brain cells. Most commonly, it begins with difficulty forming new memories, repetitive questioning, misplacing items, and forgetting recent conversations or appointments, while long-term memories are often relatively intact.
Over time, word-finding difficulties, disorientation to time or place, and difficulty with complex tasks (eg managing finances) may develop. Less commonly, the first symptoms involve language, visual-spatial skills or motor function instead of memory (atypical variants)
Over time, it can cause changes in:
- memory loss
- language changes
- personality or behaviour changes
- reasoning and planning
- loss of independence,
What happens in the brain?
Alzheimer’s disease is associated with abnormal changes in the brain, including the buildup of abnormal proteins such as amyloid plaques and tau tangles, leading to progressive loss of brain cells, typically starting in areas important for memory (the hippocampus and surrounding structures) before spreading.
These changes are associated with progressive disruption of brain function and development of symptoms associated with Alzheimer’s disease.
What increases the risk of Alzheimer’s disease?
Alzheimer’s disease does not have a single cause. Instead, a combination of factors is thought to influence a person’s risk, some of which can be changed and some of which cannot.
Factors that cannot be changed include:
- age – the strongest known risk factor, with risk increasing significantly from around age 65 onward, though Alzheimer’s disease can occur earlier (young-onset Alzheimer’s disease)
- a gene called APOE-E4 – carrying one or two copies of this gene variant is associated with a higher risk of developing Alzheimer’s disease, though carrying it doesn’t mean that dementia due to Alzheimer’s disease is inevitable
- family history and genetics – having a close relative with Alzheimer’s disease slightly increases risk. A small number of cases are linked to specific inherited genetic changes, though most cases are not directly inherited.
What risk factors may be modifiable?
Factors that may be modifiable, meaning they can potentially be reduced through lifestyle or medical care, include:
- cardiovascular health – high blood pressure, high cholesterol, diabetes, obesity and smoking are all linked to a higher risk of Alzheimer’s disease and other dementias
- education level – fewer years of formal education in early life is associated with a modestly higher risk, though this relationship is complex
- head injury – a history of significant head injury is associated with a higher risk
- hearing loss – untreated hearing loss in mid-life is associated with a higher risk, and using hearing aids where needed may help reduce this
- physical activity – regular exercise is associated with a lower risk
- sleep and mood – poor sleep quality and untreated depression have also been linked to increased risk
- social and mental engagement – social isolation and reduced mental stimulation are associated with a higher risk.
It’s important to understand that having one or more of these risk factors doesn’t mean a person will develop Alzheimer’s disease, and having none doesn’t guarantee a person won’t. Managing modifiable risk factors, particularly cardiovascular and lifestyle-related ones, is thought to help reduce overall risk, though it cannot completely prevent the disease.
Common patient questions
No. Alzheimer’s is one cause of dementia.
Some treatments may slow progression in selected patients with early Alzheimer’s disease.
Early signs commonly involve changes in:
- daily problem-solving
- learning
- short-term memory.
In Alzheimer’s disease, abnormal amyloid protein and tau protein are associated with synapse dysfunction, neuroinflammation and neuronal loss, which are processes thought to contribute to cognitive decline.
For more about brain plaque, tau tangles and neurofibrillary tangles, see amyloid protein and tau protein.
Posterior cortical atrophy is an atypical presentation of Alzheimer’s disease. Its common features include difficulty with:
- judging distances or depth
- navigating familiar environments, despite normal eyesight on standard eye tests
- reading (words seeming to move or disappear)
- recognising objects or faces
- visual-spatial tasks, often affected early in the condition.
Patients may have difficulty with everyday visually guided tasks such as dressing, using stairs or driving. Memory and insight are often relatively preserved early, which can delay diagnosis.
In the brain, amyloid and tau proteins are involved (as in typical Alzheimer’s disease), but they affect the back (occipitoparietal) regions of the brain first, rather than memory areas.