Understanding the difference between dementia and Alzheimer’s requires the acknowledgement of two important facts. The first is that Alzheimer’s disease is a form of dementia. The second is all dementia is not Alzheimer’s disease.
Dementia is a decline in a person’s cognition, which when severe interferes with the ability to perform activities of daily living without help. Cognition means mental skills. It includes such processes as knowing, recognizing, remembering, comprehending, reasoning and sometimes forming mental pictures. It is the basis for making rational judgments and decisions. It is also a process for acquiring knowledge. But it is distinct from emotion and will.
The cognitive deficits associated with Alzheimer’s disease and other forms of dementia are due to structural damage or destruction of areas of the brain. Alzheimer’s disease in general, affects the cortex of the brain, including the part that subserves memory. Other forms of dementia affect the cerebral cortex ± other areas of the brain depending upon the type of disease and how severe it is. There is some overlap in the areas of the brain that the different forms of dementia affect. This explains why many of the different types of the disease have some signs and symptoms in common.
Dementia can occur at any age, but most commonly has its onset after the age of 60. Thereafter, it becomes more frequent with increasing age. Some studies estimate that 13.9% of people 71 years of age or older have some form of dementia. An estimated 60% to 80% of all cases of dementia are Alzheimer’s disease. These figures translate into an estimated 4.7 million people 65 years of age or older in the United States. It is expected that by 2050 13.8 million people 65 years of age or older will have the disease.
Other Types of Dementia
The second most common form of dementia after Alzheimer’s disease is vascular dementia which accounts for between 20% and 30% of the cases in the United States. Other well-recognized but less common forms are:
- dementia with Lewy bodies – the second most common progressive dementia after Alzheimer’s disease
- Parkinson disease dementia
- progressive supranuclear palsy
- cortical basal degeneration
- multiple system atrophy
- frontotemporal dementia
- primary progressive aphasia
- normal pressure hydrocephalus
- Creutzfeldt-Jakob disease – the human equivalent of mad cow disease
Alzheimer’s disease and other forms of dementia in general are not curable. Many of the symptoms of Alzheimer’s disease partially respond temporarily to medications though, in contrast to most of the other forms of dementia.
Based on the broad definition of dementia, there are some forms which are treatable and potentially reversible. They include nutritional deficiencies, particularly of vitamin B-12 and vitamin B1. Other potentially reversible forms include those resulting from infections or mechanical injury to the brain, brain tumors, hormonal disorders, certain drugs, reduced oxygen and alcoholism. Also, the dementia associated with hydrocephalus is sometimes reversible with the placement of a shunt.
In terms of prognosis the most important difference between dementia and Alzheimer’s disease is the possible reversibility and lack of progression of some but not all cases of the former. In any case, a significant noticeable decline in intellectual function warrants proper medical attention.