Jun 5, 2010

Alzheimer’s Is Not Genetic (Video, Text)

By Bob DeMarco
Alzheimer's Reading Room

Question: Is Alzheimer’s inherited genetically?

Ottavio Arancio: With respect to that I have to say that less than 5% of Alzheimer’s disease are genetically transmitted, so 95% are not genetically transmitted and generally speaking the ones that are genetically transmitted they tend to occur at earlier ages than, although it is not a general rule, but more often people who have it because of genetic reasons that 5% of the people… population have it at earlier ages, but only 5% or less than 5%, about 5, around that number.

Question: Does the likelihood of acquiring Alzheimer’s vary across cultures?

Ottavio Arancio: It’s not that in China there is more than America or less or in Europe there is more or less than here and there, but there are particular populations that in particular circumstances that could lead to dementia and because of the habits of those you know populations. It’s just there are small groups of people. For instance, in the Pacific there were populations that used to eat the brain of the dead people and then they were transferring disease, which one of the symptoms of this disease was dementia and they were all developing dementia, so over there, there was a higher incidence of dementia just because this habit of eating the brain of the people that were dead the therefore like an infectious disease. They were transferring the disease and there were higher incidence of people affected by disease. Once this was found and this habit was stopped then the incidence of disease became the same as with in other populations.

Question: Who is most likely to get Alzheimer’s disease?

Ottavio Arancio: In general you know if you look at our society there is not a population of people or you know that is more affected by the loss of memory. It is a problem that hits with aging, so something related with aging and so as we age we get more memory problems. Obviously not all people are equal. There are some who have a better memory than others, and we do not know why some people have a better memory than others. I mean we say that the… if we keep ourselves and our brain exercised just like a muscle then we tend to have less memory problems, so it's kind of protective the activity or mental activity. Even some people think even physical activity it could be protective against the memory loss, you know, the loss of memory. That’s what I would have to say. Obviously there are diseases which are associated. The most typical one is Alzheimer’s disease, which are associated with the loss of memory and others, but of less relevance and less…

Question: What form of memory decreases the most with aging?

Ottavio Arancio: The characteristic symptom of Alzheimer’s disease, which is really hallmark of disease, is the loss of what we call short-term memory, so that’s how the disease starts actually. It’s people who cannot remember what they just did, just very short term memory loss and that lasts for a very, very long time and progressively the memory problem gets worse and worse and only at the very late stage or Alzheimer’s disease is when also long term memory is affected, but the major characteristic of Alzheimer’s disease, which is a very widespread disease in the population, especially at old age, is the loss of short-term memory.

OTTAVIO ARANCIO, Professor, Taub Institute for Research in Alzheimer's Disease and the Aging Brain, Columbia University

Dr.RUDY TANZI, Harvard Medical School, commented:

Dr Arrancio seems to be referring to the term "familial" (not "genetic") when he says that only 5 of Alzheimer's is genetic. In fact, twin studies show that at least 80% of Alzheimer's involves genetic factors that are inherited. This applies to both the "sporadic" cases and "familial" cases. Familial cases account for 5% of Alzheimer's are defined by clustering of the disease in a family - the patient must have two or more first degree relatives with the disease to say it is familial. But, both familial cases and sporadic cases of Alzheimer's involve the strong influence of genetic factors based on thousands of studies.

I should add that recent genome-wide association screens of many thousands of Alzheimer's cases show that the vast majority of Alzheimer's disease (the 5% that is familial and the 95% that is sporadic) involves dozens of genetic variants that influence risk over one's lifetime.

Big Think

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+Bob DeMarco  is the editor of the Alzheimer's Reading Room and an Alzheimer's caregiver. Bob has written more than 4,600 articles with more than 335,000 links on the Internet. Bob resides in Delray Beach, FL.
Original content Bob DeMarco, the Alzheimer's Reading Room