Alzheimer's disease (AD) is a progressive neurologic disorder that causes the brain to shrink (atrophy) and brain cells to die. Alzheimer's disease is the most common cause of dementia - a continuous decline in thinking, behavioral and social skills that affects a person's ability to function independently.
Approximately 5.8 million people in the United States age 65 and older live with Alzheimer's disease. Of those, 80% are 75 years old and older. Out of the approximately 50 million people worldwide with dementia, between 60% and 70% are estimated to have Alzheimer's disease.
Memory loss is the key symptom of Alzheimer's disease. Early signs include difficulty remembering recent events or conversations. As the disease progresses, memory impairments worsen and other symptoms develop.
At first, a person with Alzheimer's disease may be aware of having difficulty remembering things and organizing thoughts. A family member or friend may be more likely to notice how the symptoms worsen. People with Alzheimer's may:
Repeat statements and questions over and over
Forget conversations, appointments or events, and not remember them later
Routinely misplace possessions, often putting them in illogical locations
Get lost in familiar places
Eventually forget the names of family members and everyday objects
Have trouble finding the right words to identify objects, express thoughts or take part in conversations
Difficulties in thinking and reasoning, as well as making judgments and decisions
As AD progresses, brain changes associated with Alzheimer's disease will lead to growing trouble with many aspects mentioned above, and when it gets worse, people’s moods, mental health and behaviors will be affected, leading to depression, apathy, social withdrawal, mood swings, distrust in others, irritability/aggressiveness and eventually, paralysis and death.
The exact causes of Alzheimer's disease aren't fully understood. But at a basic level, brain proteins fail to function normally, which disrupts the work of brain cells (neurons) and triggers a series of toxic events. Neurons are damaged, lose connections to each other and eventually die.
For 1% of all cases, there are three genes that determine definitively whether or not you will have Alzheimer's, and all three relate to amyloid-beta production, which in these cases is likely the cause of Alzheimer's, according to Dr. Gad Marshall , associate medical director of clinical trials at the Center for Alzheimer Research and Treatment at Harvard-affiliated Brigham and Women's Hospital.
For the other 99%, amyloid and tau are closely associated with Alzheimer's, but many things may contribute to the development of symptoms, such as inflammation in the brain, vascular risk factors, and lifestyle. That being said, scientists believe that for most people, Alzheimer's disease is caused by a combination of genetic, lifestyle and environmental factors that affect the brain over time.
The damage most often starts in the region of the brain that controls memory, but the process begins years before the first symptoms. The loss of neurons spreads in a somewhat predictable pattern to other regions of the brains. By the late stage of the disease, the brain has shrunk significantly.
Increasing age is the greatest known risk factor for Alzheimer's disease. Alzheimer's is not a part of normal aging, but as you grow older the likelihood of developing Alzheimer's disease increases. In one study, for example, found that annually there were four new diagnoses per 1,000 people ages 65 to 74, 32 new diagnoses per 1,000 people ages 75 to 84, and 76 new diagnoses per 1,000 people age 85 and older.
【Family history and genetics】
Your risk of developing Alzheimer's is somewhat higher if a first-degree relative — your parent or sibling — has the disease. Most genetic mechanisms of Alzheimer's among families remain largely unexplained, and the genetic factors are likely complex.
One better understood genetic factor is a form of the apolipoprotein E gene (APOE). A variation of the gene, APOE e4, increases the risk of Alzheimer's disease. Approximately 25% to 30% of the population carries an APOE e4 allele, but not everyone with this variation of the gene develops the disease.
There appears to be little difference in risk between men and women, but, overall, there are more women with the disease because they generally live longer than men.
People who've had a severe head trauma have a greater risk of Alzheimer's disease. Several large studies found that in people age 50 years or older who had a traumatic brain injury (TBI), the risk of dementia and Alzheimer's disease increased. The risk increases in people with more-severe and multiple TBIs. Some studies indicate that the risk may be greatest within the first six months to two years after the TBI.
Studies in animals have indicated that air pollution particulates can speed degeneration of the nervous system. And human studies have found that air pollution exposure — particularly from traffic exhaust and burning wood — is associated with greater dementia risk.
【Lifestyle and heart health】
Research has shown that the same risk factors associated with heart disease may also increase the risk of Alzheimer's disease. These include lack of exercise, obesity, smoking/exposure to secondhand smoke, high blood pressure/cholesterol etc. In particular, excessive alcohol consumption has long been known to cause brain changes. Several large studies and reviews found that alcohol use disorders were linked to an increased risk of dementia, particularly early-onset dementia.
【Lifelong learning and social engagement】
Studies have found an association between lifelong involvement in mentally and socially stimulating activities and a reduced risk of Alzheimer's disease. Low education levels — less than a high school education — appear to be a risk factor for Alzheimer's disease.
As some of you may know, current research finds out that many biomarkers (such as proteins, shown in the graph below, in different colors) start to accumulate/lose functions as Alzheimer progresses, including Amyloid-beta, Tau etc.
Alzheimer's disease progresses in stages, and it is often broken down into 3 stages (early, middle, late). But more precisely, there is an alternate, more detailed and prevalent staging system: Reisberg Alzheimer's Scale, also known as Global Deterioration Scale (GDS). It is developed by Barry Reisberg from New York University. This scale consists of 7 major clinical stages. It is used by clinicians and in care settings. Either staging system is correct, but some clinicians use one and not the other.
In the Global Deterioration Scale, the 7 stages are further classified into 2 different categories. Stages 1 to 3 are considered the pre-dementia stages, and stages 4 to 7 are the dementia stages. Starting at stage 5, an individual cannot survive without help (also referred as advanced).
Currently, there is no proved treatment that cures Alzheimer's disease or alters the disease process in the brain for advanced stages of the disease. At advanced stages, complications from severe loss of brain function (such as dehydration, malnutrition or infection) could result in death.
But be confident! Alzheimer's disease is not a preventable condition only when it’s already advanced. If you can do early screening, assess your risks and get prepared beforehand, it will help a lot!
As we introduce previously, the early signs of the disease include forgetting recent events or conversations. As the disease progresses, a person with Alzheimer's disease will develop severe memory impairment and lose the ability to carry out everyday tasks.
Medications may temporarily improve or slow progression of symptoms. These treatments can sometimes help people with Alzheimer's disease maximize function and maintain independence for a time. Different programs and services can help support people with Alzheimer's disease and their caregivers.
Besides medication, a number of risk factors for Alzheimer's can be modified, such as lifestyle, learning and social engagement and so on, and they tend to play a significant role in AD’s progression or prevention – it’s up to what you do.
Evidence suggests that changes in diet, exercise and habits, steps to reduce the risk of cardiovascular disease, may also lower your risk of developing Alzheimer's disease and other disorders that cause dementia. Heart-healthy lifestyle choices that may reduce the risk of Alzheimer's include:
Eating a diet of fresh produce, healthy oils and foods low in saturated fat such as a Mediterranean diet
Following treatment guidelines to manage high blood pressure, diabetes and high cholesterol
Asking your doctor for help to quit smoking if you smoke
Currently, there are already many studies proving that multidomain lifestyle-based interventions (nonpharmacological interventions) helped cognitive performance in patients at risk of dementia versus regular health advice .
Besides, caregiver interventions are an important component of overall care of AD, and continued support for caregivers is instrumental in treating Alzheimer’s disease holistically [3,4]: As of 2017, 48% of caregivers were unpaid while caring for a spouse, parent, or family member. Dementia caregivers tend to provide more extensive assistance as the disease progresses, with an emphasis on self-care and mobility. The care required of family members can result in increased emotional stress and feelings of depression.
On the other hand, studies have also shown that preserved thinking skills later in life and a reduced risk of Alzheimer's disease are associated with participating in social events, reading, dancing, playing board games, creating art, playing an instrument, and other activities that require mental and social engagement.
Therefore, learn new things, play some games, practice and stimulate your thinking skills, and you can also achieve connecting socially through doing this.