Alzheimer's disease is a progressive brain disorder that causes problems with memory, thinking and behavior in older adults. The disorder affects an estimated 5.7 million Americans, and is the fifth-leading cause of death in people ages 65 and older, according to the Centers for Disease Control and Prevention (CDC).
Alzheimer's disease is often used as a synonym for dementia, which is a devastating loss of memory and cognitive function in older people, said Dr. Brad Hyman, a neurologist and director of the Massachusetts Disease Research Center at Massachusetts General Hospital in Boston. Dementia is an umbrella term for impaired memory thinking skills, and Alzheimer's is a specific form of dementia. Alzheimer's disease is responsible for 50-70% of all dementia cases, according to Alzheimers.net.
The first case of Alzheimer's was described in 1906 by Dr. Alois Alzheimer, a German neurologist. Alzheimer identified two of the disease's key physical traits when he examined a woman's brain tissue under a microscope after her death: He found abnormal protein clumps (now known as amyloid plaques) and tangled bundles of nerve fibers (now called neurofibrillary, or tau, tangles). [6 Big Mysteries of Alzheimer's Disease]
An explosion of research over the last five years has shed more light on what goes wrong in the brain during Alzheimer's, Hyman told Live Science. Four things are seen in the brain tissue of a person who has died of the disease: The two traits that Dr. Alzheimer noted, plus nerve cell loss and inflammation, he said.
The increased appearance of plaques, which are protein deposits that buildup in the spaces between nerve cells, is widely believed to be what initiates the disease in the brain, Hyman said. Twisted tangles of proteins called tau proteins can build up inside nerve cells, and along with increased numbers of plaques, can block communication between nerve cells.
The continued loss of connections between nerve cells damages them to the point that they can no longer function properly in the parts of the brain affecting memory, and the nerve cells eventually die. As more nerve cells die, parts of the brain that control reasoning, language and thinking skills are also affected, and brain tissue begins to shrink.
Researchers also suspect that inflammation (excessive action of immune cells in the brain) plays an important role in the progression of Alzheimer's and is more than a side-effect of the disease, Hyman said.
The brain changes associated with Alzheimer's may begin a decade or more before a person begins experiencing symptoms, Hyman said.
The most common early symptom of Alzheimer's is difficulty remembering newly learned information, such as recent conversations, events or people's names, according to the Alzheimer's Association. But not everyone has memory problems initially, and some people may first develop changes in their behavior, language difficulties or vision problems.
According to the Mayo Clinic, symptoms in people with mild-to-moderate forms of Alzheimer's may include:
- Repeating statements and questions over and over.
- Forgetting conversations, appointments or events, and not remembering them later.
- Routinely misplacing possessions, and frequently putting them in illogical places.
- Getting lost in familiar places.
- Forgetting the names of loved ones and everyday objects.
- Trouble finding the right words to identify objects, expressing thoughts or participating in conversations.
- Having difficulty concentrating and thinking, and managing finances.
- Struggling to do once-routine activities, such as cooking and playing a favorite game, and eventually forgetting how to do basic tasks, such as getting dressed or bathing.
Alzheimer's also causes the following mood and behavior symptoms:
- Distrusting others
- Hallucinations and delusions
- Anger, agitation and aggression
- Loss of inhibitions
- Mood swings
- Social withdrawal
- Wandering and pacing
People with advanced-stage Alzheimer's experience a severe loss of brain function and become completely dependent on others for their care. According to the National Institutes of Health, symptoms during this stage may include:
- Weight loss
- Skin infections
- Difficulty swallowing
- Groaning, moaning or grunting
- Increased sleeping
- Lack of bladder and bowel control
Causes and risk factors
The cause of Alzheimer's disease is unclear, but researchers suspect the disease is triggered by a combination of genetic, lifestyle and environmental factors that affect the brain over time.
Getting older is the biggest risk factor for developing Alzheimer's. Early-onset Alzheimer's affects people under age 60, and some forms may be inherited. But early-onset disease represents less than 10% of all people with the disorder, according to the National Institute on Aging. Late-onset Alzheimer's is the more common form of the disease, and its first symptoms may appear after age 65.
Besides age, other risk factors for Alzheimer's disease, according to the Mayo Clinic, include:
- Family History. People whose parents or siblings have Alzheimer's have a somewhat higher risk of the disease.
- Heredity. Genetic mutations, such as inheriting the apolipoprotein-E gene, can contribute to the development of Alzheimer's. (But genetic mutations account for less than 1% of people with Alzheimer's, according to the Mayo Clinic.)
- Down Syndrome. People with Down Syndrome are more at risk for Alzheimer's because they have three copies of chromosome 21, which can lead to developing more amyloid plaques in the brain.
- Mild cognitive impairment (MCI). People with MCI have more memory problems than normal for their age, but symptoms don't interfere with their lives. MCI can increase the risk of developing Alzheimer's.
- Severe head injuries. Head injuries have been linked with an increased risk of Alzheimer's.
- Low education levels. People with less than a high-school education may be at higher risk for Alzheimer's.
While there is no single test to diagnose Alzheimer's, doctors may examine a patient for signs of stroke, tumors, thyroid disorders or vitamin deficiencies as these factors also affect memory and cognition, Hyman said.
Doctors will also perform a physical exam to assess the patient's balance, muscle strength and coordination, and conduct neuropsychological tests of memory, language and basic math skills. Along with reviewing the patient's medical history, the doctor may also survey family or friends about the patient's behavior and personality changes.
In the past few years, positron emission tomography (PET) scans of the brain, which can detect whether plaques or tangles are present, have been used to diagnose or monitor the disease, especially in research, Hyman said. Another exciting breakthrough is the use of cerebrospinal fluid from a spinal tap to measure abnormal protein concentrations in the brain, which indicates the presence of Alzheimer's, he said.
There isn't a cure for Alzheimer's, but there are medications available that treat some of the symptoms of the disease, Hyman said.
Cholinesterase inhibitors are drugs that may help with symptoms such as agitation or depression. These drugs include donepezil (Aricept), galantamine (Razadyne) and rivastigmine (Exelon).
Another medication known as memantine (Namenda) may be used to slow the progression of symptoms in people with moderate to severe Alzheimer's. Some patients may be prescribed antidepressants to control behavioral symptoms.
Experts agree that in addition to medication, lifestyle factors, such as staying physically, mentally and socially active can all help the brain. A diet rich in fruits, vegetables and whole grains, with moderate amounts of fish, poultry and dairy can also be beneficial.
Alzheimer's research has expanded significantly in the past decade, Hyman said. Dozens of clinical trials are aimed at finding treatments to slow the disease progression or prevent it altogether, he said.
Previous clinical trials focused on preventing the increase in plaques in the brain, but those experimental therapies failed to produce dramatic results, Hyman said. That outcome suggests that the treatment was administered too late in the disease progression.
Instead of focusing on plaques, recent drug trials have focused on three other goals for new therapies, Hyman explained. One is to explore whether there are ways to make the brain's remaining nerve cells work better and more efficiently. The second is looking at ways to get rid of the tangles in the brain, and the third is investigating whether decreasing inflammation can prevent harmful brain changes, Hyman said.
- Read what the National Institute of Neurological Disorders and Stroke has to say about Alzheimer's disease.
- Learn more about Alzheimer's in this free book from the National Institute on Aging.
- Find out what's on the horizon in Alzheimer's treatment from the Mayo Clinic.
This article is for informational purposes only and is not meant to offer medical advice.
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