When Does Alzheimer's Disease Really Begin?
This question is prone to a wide range of answers because physicians tend to address the question based on a strict, clinical definition of Alzheimer's disease whereas scientists adhere to a different definition. The rest of the world, including journalists, tends to consider the disease more generally. Let me explain.
Consider the intersection of four groups of people who might be involved in a "discussion" about Alzheimer's disease (such as this one recently posted at WebMD). There may be (1) the scientists who study the disease, (2) the physicians who treat the disease, (3) journalists and publishers who glean information from both the scientists and physicians before packaging it for delivery to the public, and (4) the lay-persons who consume all of that information.
There are common discrepancies between how each of these groups thinks about, and in fact define Alzheimer's disease. As such, one group's answer to the question (When Does Alzheimer's Disease Really Begin?) is frequently misinterpreted by a member of another group.
The scientists tend to think in terms of disease pathology. In their minds, as soon as some biological process initiates a cascade of other processes that will eventually lead to Alzheimer's lesions in the brain, then the disease has begun.
The physicians are bound by the duty of consistency to use the definition published and accepted by their peers. Since the clinical definition of Alzheimer's disease currently requires the presence of "dementia", then physicians peg the start of the disease at the point when the patient has accumulated so much brain damage that they can no longer care for themselves without human assistance.
The journalists and publishers are adept at gathering facts and packaging them into public messages. Being unaware of these diverse definitions, they often repeat "expert testimony" without realizing the nuances therein and without clarifying the context of their statements.
The public tends to think about the disease in terms of symptoms. That is, if one has memory loss or other cognitive difficulties, perhaps there is a disease at hand affecting their brain. If one has no symptoms then they are probably in good health. This perspective would consider the start of Alzheimer's to be at the onset of noticeable memory loss. That happens much later than the scientific perspective (biological change not yet manifest in symptoms) but much earlier than the clinical perspective (severe symptoms meeting the definition of dementia).
Here are two common scenarios, both of which lead to confusion.
- A basic scientist might tell a journalist that Alzheimer's disease probably begins thirty years or so before the first symptoms appear. A healthy, lay-person reads the resulting article and worries needlessly about the prospect that they might already have the disease.
- A prominent physician might tell a journalist that patients suffering from memory loss have mild cognitive impairment and may or may not convert to Alzheimer's disease. A lay-person who is clearly in cognitive decline and needs medical attention decides that they may not yet have reached the point where they should seek help.
It really is amazing how much seemingly contradictory information is published about Alzheimer's and dementia each day when, in fact, most of the messages could be well aligned if more care were paid to definitions.