Alzheimer's is a disease that may affect many of us eventually.  I have a hard time understanding what's actually going on biologically/biochemically.  The most recent edition of Scientific American, May 2020, has an interesting set of papers.  The first one I found very illuminating, partially because it shows that researchers themselves are similarly stumped.  It also has the best statement of the main issues I that have ever read.

"Protein-Disposal Problems

"Beginning in the early 1900s, several neuropathologists -- including Alois Alzheimer [1864-1915], the scientist after whom the disease is named -- described microscopic lesions in the brains of patients who had died with various forms of dementia.  Today we know these are clumps of misshapen proteins.  In the case of Alzheimer's, some of the clumps consist of pieces of beta-amyloid protein.  They sit between neurons and are called senile plaques.  Other clumps reside within neurons, made of a protein known as tau, and are called neurofibrillary tangles.

"What we still do not know, more than a century later, is why cells fail to remove these abnormal lumps.  Cellular mechanisms for the removal of damaged proteins are as ancient as life itself.  What has gone wrong in the case of Alzheimer's?  This question is as central to the disease process as a loss of control over cell proliferation is to the progression of cancer."

This is not the whole story; for the rest of it, I suggest that you read the article.

The subsequent article is also illuminating, with the subtitle "Getting older is the biggest risk factor for Alzheimer's.  Research indicates that being female is a close second.  Why?"

The third article has the statement: "in some regions of the world, air pollution is so bad that people die of heart disease long before they would ever show symptoms of late-onset Alzheimer's."

"The Way Forward," Kenneth S. Kosik, Scientific American, May 2020, p30
"The Menopause Connection," Jena Pincott, Scientific American, May 2020, p37
"The Role of Air Pollution," Ellen Ruppel Shell, Scientific American, May 2020, p42

Gareth Hunt, 19 April 2020