A common bacterium best known for causing pneumonia and sinus infections may also play a surprising role in Alzheimer’s disease. Researchers found that Chlamydia pneumoniae can invade the retina and brain, where it sparks inflammation, nerve cell death, and the buildup of amyloid-beta—the hallmark protein linked to Alzheimer’s. Higher levels of the bacterium were found in people with Alzheimer’s, especially those carrying the high-risk APOE4 gene, and were tied to more severe cognitive decline.
