By Michael Mullan MD, PhD.
Although nothing in this document is meant to replace the attention of a well trained professional in the diagnosis and treatment of dementia, memory loss or Alzheimer's Disease, it is meant as a helpful guide to frequently asked questions that many friends and family members have asked me over the years.
Question: what is the difference between dementia and Alzheimer's Disease?
To be described as having dementia you have the have three things amiss:
1) Loss of memory
2) Loss of some other mental faculty such as the normal use of language - word finding problems or repetitiveness are examples (there are many others - see below)
3) Problems 1) and 2) are sufficiently severe to interfere with normal activities of daily living such as dressing washing attending to finances or successfully navigating to shops.
So dementia is a general term that just describes the state of the subject but it does not describe the cause.
Alzheimer's Disease is a specific type of dementia but there are many many other forms of dementia. Alzheimer's Disease has certain characteristics which distinguish it from other types of dementia and will be discussed in more detail below.
Question: What is Alzheimer's Disease?
Alzheimer's Disease is named after a German psychiatrist that first described it in a relatively young woman in 1907. However, nowadays we are most accustomed to the much more common late onset form of the disease ie when the disease occurs in those over 65 years of age. Alzheimer's Disease is known as a neurodegenerative disease which means that as the disease progresses the brain is gradually destroyed but that is in the relatively late stages of the disease. In the earlier stages not so much damage had been done to the brain and in the very early stages it is difficult to see any changes on brain scans. But what is actually happening in the brains of people with Alzheimer's Disease? Well it depends on the stage. In the very early stages there is an accumulation of a small protein called amyloid. Amyloid is a normal constituent of the brain and we all make it throughout our lives but we are able to clear it from our brains into the blood stream where it is broken down by the liver. For reasons which are not completely clear in some brains amyloid begins to accumulate and forms insoluble clumps called plaques. The accumulation of amyloid results in a lot of inflammation in the brain and over a long period this leads to destruction of neurons. As the neurons are being placed under stress from the toxic effects of the amyloid they start to lose their normal structures and start to accumulate another protein called tau. Tau has a normal function in transporting chemicals inside the neurons so when it is disrupted so are important functions of the neuron. When tau accumulates it forms structures called tangles. When neurons start to malfunction we lose our memories or the use of language, orientation and other mental faculties. So the underlying cause of all the clinical symptoms in Alzheimer's Disease is the damage caused by amyloid plaques and the tau tangles. This process takes place over many years perhaps as long as twenty in many cases. During the early stages of amyloid accumulation and even tangle formation there may be no symptoms. People have been found to have a lot of amyloid in their brains with no clinical symptoms. But generally speaking when amyloid persists for many years the other changes described here begin to take place with the inevitable decline in mental functioning.
To learn more about Dr. Michael Mullan's research please visit Roskamp Institute website or about Dr. Michael Mullan webpage