Alzheimer’s disease is a neurological disorder in which the death of brain cells causes memory loss and cognitive decline.
It is the most common type of dementia, accounting for 60 to 80 percent of cases of dementia in the United States.
In 2013, 6.8 million people in the U.S. had been diagnosed with dementia. Of these, 5 million had a diagnosis of Alzheimer’s. By 2050, the numbers are expected to double.
Alzheimer’s is a neurodegenerative disease. At first, symptoms are mild, but they become more severe over time.
Fast facts on Alzheimer’s disease
- Alzheimer’s disease is the most common type of dementia.
- It happens when plaques containing beta amyloid form in the brain.
- As symptoms worsen, it becomes harder for people to remember recent events, to reason, and to recognize people they know.
- Eventually, a person with Alzheimer’s is likely to need full-time assistance.
To receive a diagnosis of Alzheimer’s, the person must have experienced a decline in cognitive or behavioral function and performance compared with how they were previously. This decline must interfere with their ability to function at work or in usual activities.
The cognitive decline must be seen in at least two of the five symptom areas listed below:
1. Reduced ability to take in and remember new information, which can lead, for example, to:
- repetitive questions or conversations
- misplacing personal belongings
- forgetting events or appointments
- getting lost on a familiar route
2. Impairments to reasoning, complex tasking, and exercising judgment, for example:
- poor understanding of safety risks
- inability to manage finances
- poor decision-making ability
- inability to plan complex or sequential activities
3. Impaired visuospatial abilities that are not, for example, due to eye sight problems. These could be:
- inability to recognize faces or common objects or to find objects in direct view
- inability to use simple tools, for example, to orient clothing to the body
4. Impaired speaking, reading and writing, for example:
- difficulty thinking of common words while speaking, hesitations
- speech, spelling, and writing errors
5. Changes in personality and behavior, for example:
- out-of-character mood changes, including agitation, apathy, social withdrawal or a lack of interest, motivation, or initiative
- loss of empathy
- compulsive, obsessive, or socially unacceptable behavior
If the number and severity of symptoms confirm dementia, the following factors can then confirm Alzheimer’s.
- a gradual onset, over months to years, rather than hours or days
- a marked worsening of the individual’s normal level of cognition in particular areas
If symptoms begin or worsen over the course of hours or days, you should seek immediate medical attention, as this could indicate an acute illness.
Alzheimer’s is most likely when memory loss is a prominent symptom, especially in the area of learning and recalling new information.
Language problems can also be a key early symptom, for example, struggling to find the right words.
If visuospatial deficits are most prominent, these would include:
- inability to recognize objects and faces
- difficulty comprehending separate parts of a scene at once
- difficulty with reading text, known as alexia
The most prominent deficits in executive dysfunction would be to do with reasoning, judgment, and problem-solving.
Other early signs
In 2016, researchers published findings suggesting that a change in sense of humor might be an early sign of Alzheimer’s.
Recent research suggests that the features of Alzheimer’s, such as brain lesions, may already be present in midlife, even though symptoms of the disease do not appear until years later.
Early-onset Alzheimer’s disease
Early-onset familial Alzheimer’s disease can affect younger people with a family history of the disease, typically between the ages of 30 and 60 years.
It accounts for under 5 percent of all Alzheimer’s cases.
The progression of Alzheimer’s can be broken down into three main stages.
- preclinical, before symptoms appear
- mild cognitive impairment, when symptoms are mild
In addition, the Alzheimer’s Association describes seven stages along a continuum of cognitive decline, based on symptom severity.
The scale ranges from a state of no impairment, through mild and moderate decline, eventually reaching “very severe decline.”
A diagnosis does not usually become clear until stage four, described as “mild or early-stage Alzheimer’s.”
Alzheimer’s versus dementia
Dementia is an umbrella term for a range of conditions that involve a loss of cognitive functioning.
Alzheimer’s is the most common type of dementia. It involves plaques and tangles forming in the brain. Symptoms start gradually and are most likely to include a decline in cognitive function and language ability.
Other types of dementia include Huntington’s disease, Parkinson’s disease and Creutzfeldt-Jakob disease. People can have more than one type of dementia.
There is no single test for Alzheimer’s disease, so doctors will look at the signs and symptoms, take a medical history, and rule out other conditions before making a diagnosis.
They may also check the person’s neurological function, for example, by testing their balance, senses, and reflexes.
Other assessments may include a blood or urine test, a CT or MRI scan of the brain, and screening for depression.
Sometimes the symptoms of dementia are related to an inherited disorder such as Huntington’s disease, so genetic testing may be done.
After ruling out other possible conditions, the doctor will carry out cognitive and memory tests, to assess the person’s ability to think and remember.
To confirm a diagnosis of Alzheimer’s, the following must be present and severe enough to affect daily activities:
- gradual memory loss
- progressive cognitive impairment
Questions that may be asked to test cognitive ability include:
- What is your age?
- What is the time, to the nearest hour?
- What is the year?
- What is the name of the hospital or town we are in?
- Can you recognize two people, for example, the doctor, nurse, or carer?
- What is your date of birth?
- In which year did (a well-known historical event) happen?
- Name the president.
- Count backward from 20 down to 1
- Repeat an address at the end of the test that I will give you now (for example, “42 West Street”)
A number of assessment tools are available to assess cognitive function.
In some cases, genetic testing may be appropriate.
A gene known as the APOE-e4 is associated with higher chances of people over the age of 55 years developing Alzheimer’s.
Using this test early could indicate the likelihood of someone having or developing the disease. However, the test is controversial, and the results are not entirely reliable.
In the future, emerging biological tests may make it possible to assess for biomarkers in people who may be at risk of Alzheimer’s.
There is no known cure for Alzheimer’s. The death of brain cells cannot be reversed.
However, there are therapeutic interventions that can make it easier for people to live with the disease.
According to the Alzheimer’s Association, the following are important elements of dementia care:
- effective management of any conditions occurring alongside the Alzheimer’s
- activities and day-care programs
- involvement of support groups and services
No disease-modifying drugs are available for Alzheimer’s disease, but some options may reduce the symptoms and help improve quality of life.
Cholinesterase inhibitors that are approved for symptomatic relief in the U.S. include:
- Donepezil (Aricept)
- Rivastigmine (Exelon)
- Tacrine (Cognex)
A different kind of drug, memantine (Namenda), an NMDA receptor antagonist, may also be used, alone or in combination with a cholinesterase inhibitor.
The need for quality-of-life care becomes more important as the person becomes less able to live independently.
Results of a mouse study, published in Nature, suggested in 2016 that It may one day be possible to restore memories for people with early Alzheimer’s.
Causes and risk factors
Like all types of dementia, Alzheimer’s is caused by brain cell death. It is a neurodegenerative disease, which means there is progressive brain cell death that happens over time.
In a person with Alzheimer’s, the tissue has fewer and fewer nerve cells and connections.
Autopsies have shown that the nerve tissue in the brain of a person with Alzheimer’s has tiny deposits, known as plaques and tangles, that build up on the tissue.
The plaques are found between the dying brain cells, and they are made from a protein known as beta-amyloid.
The tangles occur within the nerve cells, and they are made from another protein, called tau.
Researchers do not fully understand why these changes occur. Several different factors are believed to be involved.
The Alzheimer’s Association has produced a journey of 16 slides that visualizes what happens in the process of developing Alzheimer’s disease.
Unavoidable risk factors for developing the condition include:
- a family history of Alzheimer’s
- carrying certain genes
Modifiable factors that may help prevent Alzheimer’s include:
- getting regular exercise
- maintaining a healthy cardiovascular system
- managing the risk of cardiovascular disease, diabetes, obesity, smoking, and high blood pressure
- following a varied and healthful diet
- participating in lifelong learning and cognitive training
Some studies suggest that staying mentally and socially engaged may possibly reduce the risk of Alzheimer’s.
Factors that increase the risk include:
- undergoing severe or repeated traumatic brain injuries (TBI)
- exposure to some environmental contaminants, such as toxic metals, pesticide, and industrial chemicals
To reduce the risk of TBI-related dementia, it is important always to wear a safety belt when traveling by car, to take precautions when playing contact sports, and to following health instructions and guidelines to ensure sufficient rest and recovery if an injury does occur.
A moderate TBI appears to double the risk of having dementia, while a severe TBI increases it 4.5 times.