Is Alzheimer Disease Caused by an Infection?

I am Dr Richard Isaacson, director of the Alzheimer's Prevention Clinic at Weill Cornell Medicine and New York-Presbyterian Hospital in New York City. I want to talk about the contagion theory of Alzheimer disease. Could Alzheimer disease be caused by an infection? Some very interesting research calls into question the precise etiology of Alzheimer disease.

Physicians and scientists have been taught for decades that amyloid causes Alzheimer disease. Although that may be true, different people may take different roads to developing the disease. Some people may be on the metabolic road; for example, having diabetes increases the Alzheimer disease risk twofold.^[1] What about hormones and the menopause transition? Maybe women are in the fast lane while men are sitting in traffic. These are all very interesting questions

Recently, some very exciting work has begun on the infectious theory of Alzheimer disease.^[2] For example, herpesviruses are ubiquitous. Many people have herpesvirus infections, but in some people, perhaps based on epigenetics and the environmental interaction with a person's genes, infection with the herpesvirus puts them on the fast track to Alzheimer disease.

For many years, we have thought of amyloid as the primary causative factor for Alzheimer disease. However, amyloid is also released in response to an infection in the brain.