Alzheimer's disease (AD) is a progressive neurologic disorder that causes the brain to shrink and brain cells to die. AD 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.
In early stages of AD, patients will show symptoms such as memory loss, which many mistakenly think is "normal aging" and does not take it seriously. As AD progresses, patients’ 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.
Recently, the International Alzheimer's Association reveals 10 early warning symptoms of Alzheimer's disease:
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. 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.
Global Deterioration Scale
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：
Stages 1 to 3: pre-dementia stages
stages 4 to 7: dementia stages. Starting at stage 5, an individual cannot survive without help (also referred as advanced).