Loss of Smell Linked to Early Alzheimer’s Immune Activity

Sun, 12 Apr 2026 14:03:00 +0200

Researchers from the German Center for Neurodegenerative Diseases (DZNE) and Ludwig-Maximilians-Universität München (LMU) have discovered that losing the ability to smell may be one of the first signs of Alzheimer’s disease, occurring well before memory loss starts. The study reveals how the brain’s own immune cells, known as microglia, mistakenly attack nerve fibers that connect the olfactory bulb — where scent signals from the nose are processed — to the locus coeruleus, a region in the brainstem that helps regulate sensory processing. This immune activity is triggered by changes in neuron membranes. Normally, a molecule called phosphatidylserine stays inside cell membranes, but in early Alzheimer’s it shifts to the outer surface, sending an 'eat-me' signal to microglia. As a result, these immune cells dismantle crucial connections, impairing the brain’s ability to detect odors. The research used data from mouse models, brain tissues from deceased patients, and PET scans of individua