Alzheimer's disease is difficult to diagnose because the only sure way to identify the disease is to analyze brain tissue. Taking brain tissue from a person can only be done after the person has already died. Most people are not willing to wait until someone has died to find out if they actually had Alzheimer's disease. Therefore, the diagnosis is often made on the results of many tests including:
cognitive testing (often referred to as neuropsychological testing) where a person's memory, language skills, and other mental functions are evaluated
the reports of the person or people close to the person about any changes in their thinking such as memory loss.
The Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition (DSM-5) is the technical manual used by mental health care clinicians to diagnose mental disorders. The DSM-5 upgraded the diagnosis for dementia that was used in previous versions. First, a person must meet the diagnostic criteria (diagnostic conditions or symptoms) for Mild Neurocognitive Disorder or Major Neurocognitive Disorder.
A person with Mild Neurocognitive Disorder:
Would display a decline in their thinking that is based on either:
The report of someone that knows the person very well that indicates that the person's thinking abilities have slowly declined. This could be a family member, a very close friend, or even a doctor.
Having demonstrated mild impairments on neuropsychological tests or other similar types of assessments.
The person's problems with thinking do not seriously interfere with their activities, but results in them using more energy or intentionally working harder to perform their daily activities.
A person with Major Neurocognitive Disorder would also demonstrate a decline in their thinking abilities based on a report from someone else or on formal neuropsychological testing. However, the problems with their thinking significantly interfere with their daily functioning.
A diagnosis of either Mild or Major Neurocognitive Disorder can only be made if the person's symptoms cannot be better explained by some other mental disorder such as depression or schizophrenia. The symptoms also do not happen only when the person is delirious (a temporary state of confusion that can be caused by many issues such as having an illness, being under the influence of medications or drugs, having a metabolic imbalance, etc.).
Neurocognitive disorders can have many different causes. When a diagnosis of either a Mild Neurocognitive Disorder or Major Neurocognitive Disorder is believed to be due to Alzheimer's disease the person:
Must first meet the diagnosis for either Mild or Major Neurocognitive Disorder.
Have displayed a gradual progression in one or more areas of cognition or thinking:
For mild neurocognitive disorder at least one area of thinking must be impaired.
For major neurocognitive disorder at least two areas of thinking must be impaired.
People diagnosed with Mild Neurocognitive Disorder can also be diagnosed with:
Probable Alzheimer's disease: If there is evidence that the person has genetic factors that can lead to Alzheimer's disease from genetic testing or has family members who are diagnosed with Alzheimer's disease.
Possible Alzheimer's disease: If there is no genetic evidence but there is evidence of a decline in the person's learning and memory abilities.The decline in thinking is gradual and steady. There is no evidence that other factors such as a stroke, other types of dementia, or other conditions can explain the decline in the person's memory and learning.
People diagnosed with Major Neurocognitive Disorder can also be diagnosed with:
Probable Alzheimer's disease: If the person has either:
Evidence of a genetic factor that contributes to Alzheimer's disease such as a family history of Alzheimer's disease or the results of genetic testing.
Or all of the following:
Evidence of a decline in their learning and memory and at least one other area of cognition based on neuropsychological testing or a very detailed history.
A steady, gradual, and progressive decline in memory and other areas of cognition.
No evidence of other factors that can cause dementia such as stroke or other neurological conditions.
If the above conditions are not met, then the person with Major Neurocognitive Disorder would be diagnosed with Possible Alzheimer's disease.
Major Neurocognitive Disorder is then further broken down into levels of severity:
Mild when the person's difficulties result in them having problems with what are referred to as instrumental activities of daily living (IADLs). These are basic skills that people need to live independently such as being able to pay their bills, doing housework, shopping, preparing meals, etc.
Moderate when the person's difficulties result in them having problems performing basic activities of daily living (BADLs or sometimes just ADLs). These skills represent more basic skills such as washing, dressing, etc.
Severe when the person's difficulties result in them being fully dependent on others to help them perform their basic and instrumental activities of daily living.
The diagnosis of Alzheimer's disease requires that a person has demonstrated a decline or drop in their ability to learn new information and remember things. Memory loss is the major sign that a person may be developing Alzheimer's disease. The DSM-5 also refers to other cognitive or thinking abilities that also decline in people that have the disease. Typically, memory is the first area of thinking that demonstrates a decline, but other areas of thinking also decline and can be identified in the diagnosis. These areas include:
Language Abilities: Clinicians often refer to the deterioration of language abilities as the development of aphasia. Different language abilities can be affected in Alzheimer's disease. One of the most frequent areas affected is the person's ability to name familiar objects (this is known as agnosia). Another language skill that is often affected is the person's ability to understand complex commands or to repeat phrases said to them. People with Alzheimer's disease often demonstrate "word finding difficulties" where they are trying to think of a word in conversation but cannot find it. These difficulties happen on occasion in people without Alzheimer's disease. However, people affected with the disorder display them far more frequently and their ability to function normally is significantly affected by these problems.
Attention: People affected with Alzheimer's disease often display difficulties with attention, particularly with what is referred to as complex attention. This ability involves being able to shift back and forth between objects of focus. It can also involve maintaining one's focus for an extended period of time. Again, people without Alzheimer's disease often display mild issues with these abilities. However, people with the disease display more severe and long-term issues with these abilities.
Visual spatial skills: Visual spatial abilities (also known as visuospatial abilities) refer to how a person can understand the relationships between objects in the environment and how they can view or imagine objects from different perspectives. For example, tests of these abilities often require people to copy designs, put together blocks in a specific order, or match geometric figures. These skills are used in everyday life to help us move through our environment. We use them to estimate distances between ourselves and objects or between different objects (such as when walking or driving a car). We also use them to follow instructions and put things together. They can also help us understand differences and similarities between objects.
Executive functions: This area of abilities is concerned with planning, judgment, and abstract thinking. Abstract thinking involves being able to think about things that are not actually present in the real world or to think in symbolic terms. People with Alzheimer's disease often demonstrate issues with planning or organizing activities or events, even activities that they once routinely performed.
Apraxia: This area of functioning involves the ability to perform well learned physical tasks. People with Alzheimer's disease often have difficulty performing tasks that they once were able to perform without even thinking about doing them. This could include dressing themselves, bathing, washing their clothes, tying their shoes, etc.
Neuropsychological tests can determine if a person has declined in these cognitive or thinking abilities. The results of these tests can help to diagnose Alzheimer's disease. In addition to the results of the tests, the reports of other people who are close to the person can be used. The reports can demonstrate that the person's cognitive abilities have gradually and slowly declined over time, which can also assist with the diagnosis. Clinicians prefer both the results of testing and the reports of the person or other people over either of these alone in making the diagnosis. The more evidence the clinician can gather, the more confident they can be in their ability to make the right decision as to why the person is experiencing problems with their thinking and get them treatment.
In general, the progression of Alzheimer's disease can be very rapid or very slow and research has indicated that it can take from between one to 20 years to fully progress. The average length of time that a person will have Alzheimer's disease from when it is first diagnosed until they die is about eight years. However, there is quite a bit of variation from person to person.