Alzheimer’s disease (AD) is an irreversible disease of the brain that affects a person’s memory, thinking, and other abilities. It is progressive, meaning symptoms get worse and more functions are lost the longer an individual has Alzheimer’s. Despite what some people think, getting Alzheimer’s disease is not a normal part of aging. However, it is true that people are more likely to develop AD as they age. In most cases, individuals are aged 65 and over at the time of diagnosis.
Alzheimer’s disease is the most common form of dementia in people age 65 and over. In fact, the Alzheimer’s Association has released a 2018 Alzheimer’s Disease Facts and Figures report, and one major finding is that approximately 5.7 million individuals in the United States currently have Alzheimer’s Disease. By 2050, this number is expected to reach approximately 13.8 million Americans (Alzheimer’s Association, 2018).
Causes, risk factors, and symptoms of dementia due to Alzheimer’s disease are somewhat different from other forms of dementia. With AD, the disease first attacks the memory center of the brain, which causes people to become more forgetful. As the disease progresses, the symptoms of dementia become even greater and may include issues with retaining new information, trouble concentrating, difficulty remembering the names of items and important dates, losing things and being unable to locate them, poor judgment, withdrawing from social activities, change in mood / personality, and problems with walking. Learn more about the stages of Alzheimer’s.
While there are several causes of AD, it can be quite difficult to determine the exact reason an individual is inflicted with the disease. That said, there are several risk factors for developing Alzheimer’s disease, such as age, family history, diet, and head trauma. For more information about risk factors and causes of AD, click here.
The symptoms of Alzheimer’s disease are a result of changes, both structural and cellular, in the brain.
A simple analogy helps to explain what happens in the brain when Alzheimer’s disease develops. Picture a large city with all its lights on. Each home, street, and shopping center has its own light switch and bulb that lets people go about their daily activities. From an airplane, you can see that together these lights make the entire city glow.
Now imagine that a problem occurs with the wiring or circuits within the city’s electrical system. Each home, street, and shopping center gradually loses power and the people are unable to carry on as normal. It eventually becomes harder to cook dinner, drive through the city, and do business in stores. The power outage will eventually disable the entire city and its people.
Now think about the brain: imagine that each cell within the brain is a light bulb and the entire brain is the city. Each neuron (nerve cell) helps carry out the functions of the brain. During normal function, each neuron and all the parts of the brain work together to carry out tasks such as remembering a relative’s name, washing the dishes, or controlling one’s temper.
Alzheimer’s disease gradually “turns off” each neuron in the brain, just like the lights in the city. As the individual neurons stop working, the brain does not function as well and the person has problems thinking, remembering, and carrying on with daily living. However, unlike an electrical circuit that can be repaired, damage in the brain caused by Alzheimer’s disease and dementia is permanent and cannot be repaired.
Video: Watch a short video that describes typical brain changes in dementia (1 minute 50 seconds long).
Alzheimer’s disease strikes certain parts of the brain first. The limbic system – primarily the hippocampus – is attacked first, then the cerebral cortex, then the brain stem, causing each structure to lose its function in turn. The symptoms of Alzheimer’s disease that occur are a direct result of sequential damage to the brain:
1. Limbic system (which contains the hippocampus) damage impairs a person’s memory and causes mood swings. (The limbic system is located under the cerebral cortex).
2. Cerebral cortex (part of the cerebrum) damage results in trouble controlling emotional outbursts. People at this stage may need help with daily living activities, such as eating, shaving, dressing / undressing, and combing one’s hair.
3. Brain stem damage late in AD impairs organ function, including the function of the heart, lungs, and various other bodily processes.
For more information regarding structural changes to the brain of an individual with dementia, click here.
At the cellular level, Alzheimer’s disease attacks the brain’s neurons, which are cells in the brain that carry out all brain functions. They have spaces between them called synapses. Brain chemicals, called neurotransmitters, are released by neurons and deposited into the synapses. Neurotransmitters are important for communication between neurons. This communication is responsible for producing movement and is a critical part of learning and remembering.
When cellular damage due to AD occurs, neurons cannot communicate, and learning and memory are impaired. The neurons eventually die. Because of all of this damage, the brain gradually shrinks and becomes less functional, leading to many of the symptoms of dementia.
Learn more about cellular brain changes related to Alzheimer’s disease here.
Approaches to diagnosis and treatment of Alzheimer’s disease are similar to other forms of dementia. Unfortunately, there is no cure for AD, but there are multiple treatments that can slow down the progression of the disease. According to the Alzheimer’s Association, an individual who is diagnosed with AD lives an average of 4 to 8 years after diagnosis. However, individuals can live up to 20 years after being diagnosed with the disease. Click on the following links to learn more about Diagnosing Dementia and Treating Dementia.
While an individual with Alzheimer’s disease generally has a shortened life due to the disease, it is not the direct cause of death. In the late stage of AD, the damage to the brain is so extensive the inflicted individual often no longer has mobility, causing the individual to be bed bound. These circumstances can lead to sepsis, blood clots, and infections, which may ultimately cause their death. An individual with late stage AD also has difficulty swallowing, which affects the ability to eat. Rather than swallow food into the food pipe, individuals with Alzheimer’s may swallow food into their windpipe. This can result in an infection called aspiration pneumonia, which is another cause of death of individuals with Alzheimer’s disease.