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A new breakthrough in understanding Alzheimer’s disease has provided insight into why the loss of smell is often one of its earliest symptoms—sometimes appearing even before any memory or cognitive issues. According to researchers from the German Center for Neurodegenerative Diseases (DZNE) and Ludwig-Maximilians-Universität München (LMU), the immune cells in the brain, known as microglia, may be responsible for this phenomenon.
The study, recently published in the journal Nature Communications, reveals that these immune cells mistakenly attack neuronal fibers vital for the perception of odors. This attack disrupts the connections between two crucial brain regions: the olfactory bulb and the locus coeruleus. These disruptions, observed through studies involving both mice and humans (including brain tissue samples and PET scans), help explain olfactory dysfunction as an early marker of Alzheimer’s disease.
“The locus coeruleus regulates a variety of physiological mechanisms, such as cerebral blood flow, sleep-wake cycles, and sensory processing—including the sense of smell,” explained Dr. Lars Paeger, a scientist involved in the research. According to Dr. Paeger, changes in the nerve fibers linking this brain region to the olfactory bulb signal microglia to remove what they perceive as defective connections, leading to the weakening or loss of smell.
Additionally, the research discovered that a fatty acid component known as phosphatidylserine, usually tucked away inside neuronal membranes, shifts to the outer surface in Alzheimer’s patients. This shift serves as an “eat-me” signal to the microglia, spurring them to prune away these nerve connections, a process typically reserved for removing excess or damaged neural connections during brain development.
These findings not only clarify why smell loss can precede more familiar symptoms of Alzheimer’s, but also open the door to earlier diagnosis and intervention strategies. Early detection could one day allow healthcare providers to identify individuals at risk of Alzheimer’s and begin proactive monitoring and treatment before cognitive decline begins.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Individuals concerned about Alzheimer’s or other health conditions should consult qualified medical professionals for diagnosis and treatment.
Reference: Study explains why loss of smell is linked to Alzheimer’s disease (DD News).
