Doctors categorize Alzheimer’s according to when it develops and which areas of your brain are affected. Researchers are also discovering different cellular patterns that may eventually be used to influence treatment.
Alzheimer’s disease affects an estimated 7.2 million people in the United States over the age of 65. Nearly three-quarters of people who have it are over the age of 75.
There are several different classification systems of Alzheimer’s disease. They are based on:
- the age it develops
- areas of your brain that are affected
- the presence of certain genetic markers
Additionally, researchers are looking at similar methods of studying the pathophysiology of Alzheimer’s on a cellular level and have found different patterns, which may partially explain why some people respond to certain treatments more than others.
Keep reading to learn more about the different types of Alzheimer’s disease.
Early-onset Alzheimer’s disease refers to cases in individuals under the age of 65, often appearing in people as young as their 40s or 50s.
It’s thought that early-onset Alzheimer’s makes up about 5 to 10% of cases.
The symptoms of early-onset Alzheimer’s disease are the same as later-onset Alzheimer’s and include:
- memory loss
- difficulty solving problems
- impaired judgment
- changes in mood or personality
Doctors don’t fully understand why some people develop early-onset Alzheimer’s, but they have identified some genetic markers
About 10% of cases are explainable by a known genetic mutation. Known genetic mutations linked to early-onset Alzheimer’s include those in the following
- PSEN1
- PSEN2
- APP
Diagnosing early-onset Alzheimer’s can be challenging, as symptoms are sometimes mistaken for other medical conditions.
Late-onset Alzheimer’s disease refers to the typical age of onset, which is over age 65. Anyone who does not have early onset Alzheimer’s disease would fall into the late-onset category.
Often, the first noticeable symptoms include:
- forgetting recent conversations
- misplacing items
- having difficulty with words.
Late-onset Alzheimer’s generally progresses gradually. However, some people have a rapid progression over just a few months, while others have a slow decline over many years.
As the disease advances, individuals may become disoriented, experience confusion about time or place, and require increasing support with routine activities.
As with early-onset Alzheimer’s, the exact cause is unknown. It’s believed to develop due to a mix of genetic, environmental, and lifestyle factors.
The apolipoprotein E (APOE) ε4 gene variant is the strongest known genetic risk factor for Alzheimer’s disease, but not everyone with this gene variant will develop Alzheimer’s.
Most people with Alzheimer’s have problems with their memory as one of their first symptoms. People with atypical Alzheimer’s may also have other symptoms that become more prominent, such as behavioral changes and vision changes.
Atypical Alzheimer’s can be broken into two types:
- Frontal variant Alzheimer’s disease: For about 1 in 50 people with Alzheimer’s, the disease starts in the frontal lobe. It may cause behavioral symptoms and problems with “executive function,” which includes planning, flexible thinking, and self-control. Initial symptoms might include:
- losing social inhibitions
- losing motivation
- losing the ability to understand how others are thinking or feeling
- repetitive or compulsive ritualized behaviors
- Changes to eating habits
- Posterior cortical atrophy (Benson syndrome). In people with Benson syndrome, the disease starts in the back of the brain in the visual cortex. The initial symptoms are often problems with vision, such as:
- difficulty recognizing faces, objects, or pictures
- difficulty judging distances
- problems with spatial awareness
It’s worth noting that while Alzheimer’s disease is the most common cause of posterior cortical atrophy (Benson syndrome), the condition can be caused by other things as well, including:
- multisystem atrophy
- head trauma
- stroke
- encephalitis
In a new
The subtypes that they identified include the following:
- Hyperplasticity: This subtype is characterized by excessive proteins in the brain called tau. Antibody treatments may be most effective for treating this type.
- Innate Immune Activation: In this subtype, the body’s natural immune response is heightened, leading to chronic inflammation in the brain. This inflammatory process contributes to neuronal damage. The most effective treatments may be those that target the immune system.
- RNA Dysregulation: In this subtype, disruptions in genetic messaging lead to the brain’s overproduction of proteins. Targeted therapies might involve correcting or compensating for errors in RNA function.
- Choroid Plexus Dysfunction: This subtype is characterized by a disruption in the brain’s blood vessels and slow brain cell growth. It typically leads to the worst brain shrinkage of any of the subtypes.
- Blood-Brain Barrier Dysfunction: This subtype is characterized by a problem with the brain’s blood-brain barrier, leading to microbleeds and impaired brain cell growth. The ideal treatment might include cerebrovascular drugs.
Other research groups have also attempted to define patterns in the underlying physiological processes that cause Alzheimer’s disease, as described in this
Alzheimer’s disease is divided into early-onset, when it develops under the age of 65, and late-onset, when it develops after this age.
There are also atypical forms of the disease, which have a more prominent effect on different areas of the brain.
Researchers are now discovering protein and immune changes in the brain that can help define different subtypes of Alzheimer’s disease. This field of research continues to expand, and scientists are continuing to look for ways to tailor treatment precisely between individuals.