Alzheimer’s disease is the most common form of dementia. For many years, researchers believed that its main cause was a buildup of toxic proteins. But recent findings suggest that the problem may have another origin, specifically in the bloodstream.

Contrary to a commonly held belief, dementia isn’t just about memory. Imagine the brain as a car. To run properly, this complex system depends, among other things, on an engine (our neurons, the central component) and a set of pipes (our cerebral vascular system) to deliver fuel (oxygen and nutrients) to the engine.

This article is part of our ongoing series The Grey Revolution. The Conversation Canada and La Conversation are exploring the impact of the aging boomer generation on Canadian society, including housing, working, culture, nutrition, travelling and health care. The series explores the upheavals already underway and those looming ahead.

As we age, this machinery wears out. If the pipes become damaged, rust sets in. If the engine breaks down, it affects the vehicle’s performance and inevitably leads to premature failure. In the case of Alzheimer’s disease, the “rust” is characterized by the accumulation of two toxic proteins: amyloid plaques and tau fibres, which bring about a decline in cognitive abilities, including memory.

However, several observations call into question the role of these proteins. It becomes essential to identify the cause of this “rust” and understand its origin.

The amyloid hypothesis

For many years, pharmaceutical research on Alzheimer’s disease has focused on the amyloid hypothesis, which is one form of “rust.” According to this hypothesis, the accumulation of Beta-amyloid proteins in the brain, in the form of plaques, is believed to be the primary cause of dementia.

Beta-amyloid protein is cleared naturally by the blood and lymphatic systems, or is eliminated within the brain by protective cells (microglia and astrocytes) and enzymes. A malfunction in these cleanup mechanisms,........

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