Alzheimer's Disease is difficult to diagnose because symptoms frequently resemble the symptoms of many other diseases, such as the dementias mentioned earlier (e.g., Vascular Dementia, Lewy Body Dementia). To attempt address this difficulty in diagnosing AD, the DSM-IV contains a detailed set of criteria that must be met in order for someone to receive the diagnosis.
First, the person must display multiple cognitive deficits, one of which must be memory impairment. In addition to problems with memory, the person must also have one or more of the following symptoms:
- Aphasia - This is a deterioration of language abilities, which can look different across different people. For example, individuals might have difficulty coming up with the correct names for people or objects that were previously familiar (e.g., they might not be able to remember that an object is called a "key"). People with AD often have vague speech, using the words "it" or "whatchamacallit" excessively. They may also have difficulty understanding what is being said to them, repeating back what has been heard, or comprehending what they read. In the later stages of the disease, people with Alzheimer's Disease might repeat a specific word or sound over and over, or echo things that they just heard.
- Apraxia - This is a problem with motor activities, even though people's movement, senses, and ability to comprehend language are still intact. Apraxia is basically a disconnect between the idea of a performing a task (I want to do it) and the execution of it (I can't remember how to do it). For example, individuals with Alzheimer's may have the physical and sensory abilities necessary to button a coat, but there is a mental gap between wanting to button the coat and actually being able to do it. As you can imagine, apraxia often affects the ability to carry out daily tasks such as cooking, dressing, and grooming.
- Agnosia - This is an impaired ability to recognize or identify objects, even though sensory abilities are intact. For example, people with Alzheimer's might have adequate vision but cannot correctly identify what they are seeing as a lamp. Or, they might not be able to identify a coin by touch even though they have adequate sensation in their hands. Agnosia can lead to an inability to recognize family members or one's own reflection in the mirror.
- Problems with executive functioning interfere with activities such as planning tasks, making decisions, organizing projects, or carrying out activities in the proper sequence. For example, a person with Alzheimer's who once hosted large dinner parties on a regular basis would gradually become unable to organize, plan, and carry out the tasks associated with making dinner for a small family (or him or herself).
According to the DSM-IV, in order to meet the criteria for an Alzheimer's disease diagnosis, a person's cognitive deficits must cause significant impairment in occupational and/or social functioning. In other words, the impairments must affect one's ability to hold a job or volunteer position, carry out daily life/work tasks, and/or maintain social relationships. The deficits must also be a significant decline from the person's previous level of functioning.
Also, in order to receive a diagnosis of Alzheimer's, a person's symptoms must not be caused by another medical condition, such as an central nervous system disorder (e.g., Parkinson's Disease), systemic conditions (e.g., thyroid problem, infection), or a substance-related condition (e.g., alcoholism). In addition, the cognitive deficits must not occur exclusively during an episode of delirium (a temporary cognitive disorder covered later in this paper). Finally, the deficits should not be caused by another mental disorder, such as depression or schizophrenia.