Dementia is a general term that refers to a decline in cognitive function so extensive that it interferes with daily life and activities. This loss in the ability to think, remember, and reason is not a disease itself, but a group of symptoms that often accompanies a disease or condition.
Many conditions and diseases cause dementia. Two of the most common causes of dementia in older people are AD and vascular dementia, which is caused by a series of strokes or changes in the brain’s blood supply.
Other conditions that cause memory loss or dementia include:
• medication side effects
• chronic alcoholism
• certain tumors and infections in the brain
• blood clots in the brain
• vitamin B12 deficiency
• high fever
• some thyroid, kidney, or liver disorders
Many of these conditions are temporary and reversible, but they can be serious and should be treated by a doctor as soon as possible.
Emotional problems, such as stress, anxiety, or depression, can make a person more forgetful and can be mistaken for dementia. Someone may feel sad, lonely, worried, or bored when facing retirement or coping with the death of a spouse, relative, or friend. Adapting to these changes leaves some people feeling confused or forgetful. Supportive friends and family or professional help from a doctor or counselor can help older adults adjust to big changes.
What is mild cognitive impairment?
Mild cognitive impairment (MCI) is a condition in which a person has memory problems greater than those expected for his or her age. However, people with MCI do not have the personality changes or cognitive problems that characterize AD.
MCI has several types. The type most associated with memory loss is called amnestic MCI. People with this condition have more memory problems than normal for their age, but their symptoms are not as severe as those of people with AD. More people with MCI go on to develop AD than those without MCI within a certain time frame. However, not everyone who has MCI develops AD. Studies are underway to learn why some people with MCI progress to AD and others do not.
What is Alzheimer's disease (AD)?
Alzheimer’s disease (AD) is an irreversible, progressive brain disease that slowly destroys memory and thinking skills and, eventually, the ability to carry out the simplest tasks of daily living. In most people with AD, symptoms first appear after age 60.
AD is the most common cause of dementia among older people, but it is not a normal part of aging. Dementia refers to a decline in cognitive function that interferes with daily life and activities. AD starts in a region of the brain that affects recent memory, then gradually spreads to other parts of the brain. Although treatment can slow the progression of AD and help manage its symptoms in some people, currently there is no cure for this devastating disease.
AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer described changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps (now called amyloid plaques) and tangled bundles of fibers (now called neurofibrillary tangles).
Today, these plaques and tangles in the brain are considered hallmarks of AD. The third main feature of AD is the gradual loss of connections between nerve cells (neurons) in the brain. This loss leads to diminished cell function and cell death.
We don’t know what starts the AD process, but we do know that damage to the brain begins as many as 10 to 20 years before any obvious signs of forgetfulness appear.
As nerve cells die throughout the brain, affected regions begin to shrink. By the final stage of AD, damage is widespread, and brain tissue has shrunk significantly.
How is AD diagnosed?
The only definite way to diagnose AD is with an autopsy, which is an examination of the body done after a person dies. However, doctors can determine fairly accurately whether a person who is having memory problems has “possible AD” (the symptoms may be due to another cause) or “probable AD” (no other cause for the symptoms can be found). To diagnose AD, doctors:
• ask questions about a person’s overall health, past medical problems, ability to carry out daily activities, and changes in behavior and personality
• conduct tests of memory, problem solving, attention, counting, and language skills
• carry out medical tests, such as tests of blood, urine, or spinal fluid
• perform brain scans, such as a computed tomography (CT) scan or magnetic resonance imaging (MRI) test
These tests may be repeated to give doctors information about how the person’s memory is changing over time. Sometimes these tests help doctors find other possible causes of the person's symptoms. For example, thyroid problems, drug reactions, depression, brain tumors, and blood-vessel disease in the brain can cause AD-like symptoms. Some of these other conditions can be treated successfully.
How is AD treated?
AD is a complex disease, and no single “magic bullet” is likely to prevent or cure it. That’s why current treatments focus on several different issues, including helping people maintain mental function, managing behavioral symptoms, and slowing AD.
AD research has developed to a point where scientists can look beyond treating symptoms to think about delaying or preventing AD by addressing the underlying disease process. Scientists are looking at many possible interventions, such as treatments for heart disease and type 2 diabetes, immunization therapy, cognitive training, changes in diet, and physical activity.
What drugs are currently available to treat AD?
No treatment has been proven to stop AD. The U.S. Food and Drug Administration has approved four drugs to treat AD. For people with mild or moderate AD, donepezil (Aricept®), rivastigmine (Exelon®), or galantamine (Razadyne®) may help maintain cognitive abilities and help control certain behavioral symptoms for a few months to a few years. Donepezil can be used for severe AD, too. Another drug, memantine (Namenda®), is used to treat moderate to severe AD. However, these drugs don’t stop or reverse AD and appear to help patients only for months to a few years.
These drugs work by regulating neurotransmitters, the chemicals that transmit messages between neurons. They may help maintain thinking, memory, and speaking skills and may help with certain behavioral problems.
Other medicines may ease the behavioral symptoms of AD—sleeplessness, agitation, wandering, anxiety, anger, and depression. Treating these symptoms often makes patients more comfortable and makes their care easier for caregivers.
No published study directly compares the four approved AD drugs. Because they work in a similar way, it is not expected that switching from one of these drugs to another will produce significantly different results. However, an AD patient may respond better to one drug than another.