Alzheimer’s disease

Alzheimer’s disease (AD) is a slowly progressive neurological disorder that is characterized by impairment of memory and eventually by disturbances in reasoning, planning, language, and perception. In Alzheimer’s disease death of brain cells causes memory loss and cognitive decline. Many scientists believe that Alzheimer’s disease results from an increase in the production or accumulation of a specific protein (beta-amyloid protein) in the brain that leads to nerve cell death.

Alzheimer’s disease is the most common cause of dementia – a group of brain disorders that cause the loss of intellectual and social skills. In Alzheimer’s disease, the brain cells degenerate and die, causing a steady decline in memory and mental function.

Contents of this article:

  1. Causes of Alzheimer’s Disease
  2. Stages and Symptoms of Alzheimer’s Disease
  3. How Common is Alzheimer’s Disease?
  4. Risk Factors of Alzheimer’s Disease
  5. Tests and Diagnosis
  6. Treatment and Prevention

 

Causes of Alzheimer’s Disease:

Alzheimer’s disease is caused by parts of the brain shrinking (atrophy), which affects the structure and function of particular brain areas.

It’s not known exactly what causes this process to begin. However, in the brains of people with Alzheimer’s disease, scientists have found amyloid plaques (abnormal deposits of protein), neurofibrillary tangles (containing tau) and imbalances in a chemical called acetylcholine.

  • Plaques. These clumps of a protein called beta-amyloid may damage and destroy brain cells in several ways, including interfering with cell-to-cell communication. Although the ultimate cause of brain-cell death in Alzheimer’s isn’t known, the collection of beta-amyloid on the outside of brain cells is a prime suspect.
  • Tangles. Brain cells depend on an internal support and transport system to carry nutrients and other essential materials throughout their long extensions. This system requires the normal structure and functioning of a protein called tau.
  • In Alzheimer’s, threads of tau protein twist into abnormal tangles inside brain cells, leading to failure of the transport system. This failure is also strongly implicated in the decline and death of brain cells.It’s also common to have a degree of vascular damage in the brain. These reduce the effectiveness of healthy neurons (nerve cells that carry messages to and from the brain), gradually destroying them. Over time, this damage spreads to several areas of the brain. The first areas affected are responsible for memories.

Stages and Symptoms of Alzheimer’s Disease:

The symptoms of Alzheimer’s disease worsen over time, although the rate at which the disease progresses varies. On average, a person with Alzheimer’s lives four to eight years after diagnosis, but can live as long as 20 years, depending on other factors.

The stages below provide an overall idea of how abilities change once symptoms appear and should only be used as a general guide. They are separated into three different categories: mild Alzheimer’s disease, moderate Alzheimer’s disease and severe Alzheimer’s disease. Be aware that it may be difficult to place a person with Alzheimer’s in a specific stage as stages may overlap.

Mild Alzheimer’s disease (early-stage)

In the early stage of Alzheimer’s, a person may function independently. He or she may still drive, work and be part of social activities. Despite this, the person may feel as if he or she is having memory lapses, such as forgetting familiar words or the location of everyday objects.

Friends, family or others close to the individual begin to notice difficulties. During a detailed medical interview, doctors may be able to detect problems in memory or concentration. Common difficulties include:

  • Problems coming up with the right word or name
  • Trouble remembering names when introduced to new people
  • Challenges performing tasks in social or work settings.
  • Forgetting material that one has just read
  • Losing or misplacing a valuable object
  • Increasing trouble with planning or organizing

Moderate Alzheimer’s disease (middle-stage)

Moderate Alzheimer’s is typically the longest stage and can last for many years. As the disease progresses, the person with Alzheimer’s will require a greater level of care.

You may notice the person with Alzheimer’s confusing words, getting frustrated or angry, or acting in unexpected ways, such as refusing to bathe. Damage to nerve cells in the brain can make it difficult to express thoughts and perform routine tasks.

At this point, symptoms will be noticeable to others and may include:

  • Forgetfulness of events or about one’s own personal history
  • Feeling moody or withdrawn, especially in socially or mentally challenging situations
  • Being unable to recall their own address or telephone number or the high school or college from which they graduated
  • Confusion about where they are or what day it is
  • The need for help choosing proper clothing for the season or the occasion
  • Trouble controlling bladder and bowels in some individuals
  • Changes in sleep patterns, such as sleeping during the day and becoming restless at night
  • An increased risk of wandering and becoming lost
  • Personality and behavioral changes, including suspiciousness and delusions or compulsive, repetitive behavior like hand-wringing or tissue shredding

Severe Alzheimer’s disease (late-stage)

In the final stage of this disease, individuals lose the ability to respond to their environment, to carry on a conversation and, eventually, to control movement. They may still say words or phrases, but communicating pain becomes difficult. As memory and cognitive skills continue to worsen, significant personality changes may take place and individuals need extensive help with daily activities.

At this stage, individuals may:

  • Need round-the-clock assistance with daily activities and personal care
  • Lose awareness of recent experiences as well as of their surroundings
  • Experience changes in physical abilities, including the ability to walk, sit and, eventually, swallow
  • Have increasing difficulty communicating
  • Become vulnerable to infections, especially pneumonia

How Common is Alzheimer’s Disease?

  • Worldwide, nearly 44 million people have Alzheimer’s or a related dementia. (Alzheimer’s Disease International)
  • Only 1-in-4 people with Alzheimer’s disease have been diagnosed. (Alzheimer’s Disease International)
  • Alzheimer’s and dementia is most common in Western Europe (North America is close behind).
  • Alzheimer’s is least prevalent in Sub-Saharan Africa. (Alzheimer’s Disease International)
  • Alzheimer’s and other dementias are the top cause for disabilities in later life. (Alzheimer’s Disease International)

Risk Factors of Alzheimer’s Disease:

Some things are more commonly associated with Alzheimer’s disease – not seen so often in people without the disorder. These factors may therefore have some direct connection. Some are preventable or modifiable factors (for example, reducing the risk of diabetes or heart disease may in turn cut the risk of dementia).

If researchers gain more understanding of the risk factors, or scientifically prove any “cause” relationships for Alzheimer’s, this could help to find ways to prevent it or develop treatments.

Risk factors associated with Alzheimer’s disease include:

Unavoidable risk factors

  • Age – the disorder is more likely in older people, and a greater proportion of over-85-year-olds have it than of over-65s.
  • Family history (inheritance of genes) – having Alzheimer’s in the family is associated with higher risk. This is the second biggest risk factor after age.
  • Having a certain gene (the apolipoprotein E or APOE gene) puts a person, depending on their specific genetics, at three to eight times more risk than a person without the gene.6 Numerous other genes have been found to be associated with Alzheimer’s disease, even recently (see developments below).

Potentially avoidable or modifiable factors

  • Factors that increase blood vessel (vascular) risk – including diabetes, high cholesterol and high blood pressure. (These also increase the risk of stroke, which itself can lead to another type of dementia.)
  • Low educational and occupational attainment.
  • Prior head injury. (While a traumatic brain injury does not necessarily lead to Alzheimer’s, some research links have been drawn, with increasing risk tied to the severity of trauma history.)
  • Sleep disorders (the breathing problem sleep apnea, for example).

Tests and Diagnosis:

There’s no specific test today that confirms you have Alzheimer’s disease. Your doctor will make a judgment about whether Alzheimer’s is the most likely cause of your symptoms based on the information you provide and results of various tests that can help clarify the diagnosis.

Doctors can nearly always determine whether you have dementia, and they can often identify whether your dementia is due to Alzheimer’s disease. Alzheimer’s disease can be diagnosed with complete accuracy only after death, when microscopic examination of the brain reveals the characteristic plaques and tangles.

To help distinguish Alzheimer’s disease from other causes of memory loss, doctors now typically rely on the following types of tests.

Physical and neurological exam

Your doctor will perform a physical exam, and is likely to check your overall neurological health by testing your:

  • Reflexes
  • Muscle tone and strength
  • Ability to get up from a chair and walk across the room
  • Sense of sight and hearing
  • Coordination
  • Balance

Lab tests

Blood tests may help your doctor rule out other potential causes of memory loss and confusion, such as thyroid disorders or vitamin deficiencies.

Mental status and neuropsychological testing

Your doctor may conduct a brief mental status test to assess your memory and other thinking skills. In addition, your doctor may suggest a more extensive assessment of your thinking and memory. Longer forms of neuropsychological testing may provide additional details about your mental function compared with others’ of a similar age and education level.

Brain imaging

Images of the brain are now used chiefly to pinpoint visible abnormalities related to conditions other than Alzheimer’s disease – such as strokes, trauma or tumors – that may cause cognitive change. New imaging applications – currently used primarily in major medical centers or in clinical trials – may enable doctors to detect specific brain changes caused by Alzheimer’s.

Brain-imaging technologies include:

  • Magnetic resonance imaging (MRI). An MRI uses radio waves and a strong magnetic field to produce detailed images of your brain. MRIs are used to rule out other conditions that may account for or be adding to cognitive symptoms. In addition, they may be used to assess whether shrinkage in brain regions implicated in Alzheimer’s disease has occurred.
  • Computerized tomography (CT). A CT scan produces cross-sectional images (slices) of your brain. It’s currently used chiefly to rule out tumors, strokes and head injuries.
  • Positron emission tomography (PET). During a PET scan, you’ll be injected in a vein with a low-level radioactive tracer. The tracer may be a special form of glucose (sugar) that shows overall activity in various brain regions.

This can show which parts of your brain aren’t functioning well. New PET techniques are able to detect your brain level of plaques (amyloid) and tangles (tau), the two hallmark abnormalities linked to Alzheimer’s. However, these new PET techniques are generally found in research settings or in clinical trials.

  • Cerebrospinal fluid. In special circumstances such as rapidly progressive dementia or very young onset dementia, a cerebrospinal fluid examination may be performed. The spinal fluid can be tested for biomarkers that indicate the likelihood of Alzheimer’s disease.

Future diagnostic tests

Researchers are working with doctors to develop new diagnostic tools to help definitively diagnose Alzheimer’s. Another important goal is to detect the disease before it causes the symptoms.

New tools under investigation include:

  • Additional approaches to brain imaging
  • More-sensitive tests of mental abilities
  • Measurement of key proteins or protein patterns in blood or spinal fluid (biomarkers)

Genetic testing generally isn’t recommended for a routine Alzheimer’s disease evaluation. The exception is people who have a history of early-onset Alzheimer’s disease. However, anyone with a family history of early Alzheimer’s needs to meet with a genetic counselor to discuss the risks and benefits of genetic testing.

Treatment and Prevention

There is no known cure for Alzheimer’s disease – the death of brain cells in the dementia cannot be halted or reversed.

There is, however, much backing for therapeutic interventions to help people live with Alzheimer’s disease more ably.

The Alzheimer’s Association includes the following as important elements of dementia care:

  • Effective management of any conditions occurring alongside the Alzheimer’s
  • Activities and/or programs of adult day care
  • Support groups and services.

Along with an aim to improve research into prevention and treatment, the goals of the plan also include measures for present interventions:

  • “Enhance care quality and efficiency
  • Expand supports for people with Alzheimer’s disease and their families, and
  • Enhance public awareness and engagement.”

Drug therapy

There are no disease-modifying drugs available for Alzheimer’s disease but some options may reduce its symptoms and help improve quality of life. There are four drugs in a class called cholinesterase inhibitor approved for symptomatic relief in the US:

  • Donepezil (brand name Aricept)
  • Alantamine (Reminyl)
  • 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.

Other therapy

As with other types of dementia and neurodegenerative disease, a major part of therapy for patients with Alzheimer’s comes from the support given by healthcare workers to provide dementia quality-of-life care, which becomes more important as needs increase with declining independence.

Prevention

There is a lot of research into risk factors associated with Alzheimer’s disease, so there may be lifestyle measures we can take to potentially reduce our risk and enjoy a healthier life more generally. Medical News Today has a page compiling ideas from researchers on how to prevent Alzheimer’s disease and dementia – including information about heart health, diet, exercise and keeping an active brain.