Understanding the differences between dementia and Alzheimer's disease can be confusing, especially because the two are linked in many ways and it is often difficult to get a conclusive diagnosis. The primary differences between dementia and Alzheimer's disease relate to how these terms are defined, the typical age of onset, and the course of the illness.
Definitions
Dementia is defined as a variety of cognitive deficits, which means problems with the mental processes of thinking and learning, that can result in a number of symptoms, including a decline in intellectual functioning, memory, and personality. It is a group of symptoms that relate to a set of illnesses, such as vascular dementia or dementia due to Parkinson's disease. Alzheimer's disease is one such illness. Alzheimer's disease is a type of dementia, and is thought to be the most common cause of dementia in the elderly.
In other words, dementia is a set of cognitive deficits that serves as an overarching classification for a number of illnesses. These illnesses may share common symptoms of dementia but have different underlying causes. Alzheimer's disease is a specific disease that is a type of dementia.
Age of Onset
Another difference between Alzheimer's disease and general dementia is that the age of onset for Alzheimer's disease is typically later in life. It is most common after 65 years of age; and the presence of symptoms before the age of 50 is rarely seen.
In contrast, many other forms of dementia can have an earlier age of onset. For example, individuals with dementia due to a head trauma or medical illness may show signs of dementia at a much younger age.
Course
The course of Alzheimer's disease is typically slowly progressive, without many exceptions. However, other types of dementia may have different courses of progression. Some other types of dementia may even remain unchanged or even improve.
For instance, the course and symptoms of vascular dementia may change rapidly and in an abrupt, patchy manner. The same is true for dementia due to Creutzfeldt-Jakob disease, which is characterized by a rapid progression.
The prognosis of dementia due to a medical illness or head injury may also differ from Alzheimer's disease. Alzheimer's disease typically progresses from mild to severe deficits and can lead to death.These other types of dementia may remain largely unchanged over time, and some symptoms may improve given the underlying cause of the dementia and its treatment.
References
- "Diagnostic and Statistical Manual of Mental Disorders -- Fourth Edition -- Text Revision"; American Psychiatric Association; 2000
- iHealth Directory: Dementia vs. Alzheimer's disease
