Interesting. Further research is clearly needed, particularly about the direction of causality.
Doctors from the International Alzheimer Research Center in Switzerland published a study indicating a high probability of a causal relationship, not just an association, between spirochete infections and Alzheimer’s disease.
What they discovered was pretty amazing. They found spirochetes in about 90% of Alzheimer’s patients, while the bacteria were virtually absent in healthy age-matched controls. [footnote omitted]
See also Paul Jaminet's posts "Is Alzheimer’s Caused By a Bacterial Infection of the Brain?" and "Eleven Steps for Overcoming Alzheimer’s and Other Chronic Infectious Diseases".
UPDATE: First link fixed now. Thanks, Brent.