Is every dementia the same as Alzheimer's disease?

Dementia is not a specific disease. It is the description of any progressive disorder that takes away a patient’s cognitive and functional abilities. Approximately 3.4 million people age 71 and older in the United States have dementia, and an estimated 5.3 million Americans of all ages have Alzheimer’s disease. Almost 18 million people worldwide have the degenerative disease. 

The most common cause of dementia among people age 65 and older is Alzheimer’s disease, but a number of other conditions, such as frontotemporal dementia, dementia with Lewy bodies, Jakob-Creutzfeldt disease, head trauma, stroke, or vitamin B12 deficiency can cause dementia. The damage caused by each of these diseases creates a typical pattern of cognitive loss due to the areas of the brain affected by the underlying disease. 

While dementia often includes memory loss, memory loss by itself does not mean someone has dementia. Some forms of dementia do not initially affect memory. Frontotemporal dementia is one such dementia where memory can be completely spared. These patients exhibit disruption of social behavior, overeating, apathy and personality change. By contrast, dementia with Lewy bodies patients experience visual hallucinations, fluctuating attention and exhibit progressive Parkinsonism. Jakob-Creutzfeldt disease is rapidly progressive and can go from the first symptoms to death in less than three months. 

All of these diseases are caused by a tendency for certain otherwise normal proteins to aggregate into clumps and spread within brain circuitry. In Alzheimer’s disease the two proteins are tau and a-beta-42. With frontotemporal dementia, TDP-43, tau, and FUS are the major proteins.