New triggers found for Alzheimer's

Tom Blackwell, National Post

For decades, scientists have struggled to understand what causes Alzheimer's disease, once even suspecting that exposure to aluminum pots and pans played a role. Much is still unknown.

New Canadian research, however, offers a novel clue, concluding that infectious diseases such as bacterial pneumonia and the virus behind cold sores may make people more susceptible to the devastating illness - and indicate a way to guard against Alzheimer's.

If borne out with more study, the findings would make it even more important to aggressively treat infection, while raising the possibility that vaccines against certain bacteria or viruses could actually prevent Alzheimer's, says a paper published in the journal Alzheimer's and Dementia.

"It is kind of counter-intuitive. You think an infection is gone and that is it, right?" said Dr. Paul Verhoeff, a psychiatrist at Toronto's Baycrest brain-research facility. "But think about those cold sores. Whenever your immune system is compromised, those cold sores come back ... We think that some infections can really increase the chance someone could develop Alzheimer's if the person already has other predisposing factors."

About 500,000 Canadians suffer from Alzheimer's disease and that number is expected to double within 25 years, with women being disproportionately afflicted. The main known risk factors for the degenerative brain condition include old age, diabetes, family history and cardiovascular disease.

Dr. Verhoeff and colleagues at Toronto's Sunnybrook Health Sciences Centre reviewed several studies conducted over the last decade or so that explored a link between various infections and Alzheimer's.

The most convincing evidence involves Chlamydia pneumoniae, a common bacteria estimated to be present in more than half of American adults and to cause 10-20% of the pneumonia cases outside of hospital.

One autopsy-based study found the bug in the brains of 90% of 19 Alzheimer's patients, and in just 5% of the brains of non-Alzheimer's subjects. Another detected the bacteria located close to the amyloid plaques considered a hallmark of Alzheimer's brains.

The C. pneumoniae microbe does not appear to cause the disease, but may make people more vulnerable to it and accelerate the progress of Alzheimer's, the researchers concluded.

Other studies have unearthed a link between the Herpes simplex virus - another widespread bug that causes cold sores - and Alzheimer's in people with APOE-4, a gene that itself is a risk factor for the disease.

How those and other infections might speed on the onset of Alzheimer's is unclear, but is likely related to the inflammatory effects of the pathogens, Dr. Verhoeff said.

It could be that treating infection will one day help.......read all of New triggers found for Alzheimer's

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