A new study suggests that a loss of smell could be one of the earliest warning signs of Alzheimer’s disease, appearing even before noticeable memory decline.
The findings were published in the journal Nature Communications and highlight how early brain changes may affect sensory function.
Researchers say that reduced or lost sense of smell may signal the early stages of Alzheimer’s disease.
The study found that this symptom can appear before the more commonly recognized memory-related issues begin to develop.
How brain is affected
Scientists from the DZNE research institute and Ludwig-Maximilians-University Munich (LMU) in Germany found that the brain’s immune system may play a central role in this process.
They discovered that immune cells in the brain, known as microglia, may mistakenly attack nerve fibers essential for the sense of smell.
Disruption in smell pathways
The research explains that smell problems occur when microglia disrupt communication between two key brain areas:
- The olfactory bulb, which processes smell signals from the nose
- The locus ceruleus, which helps regulate this process through nerve connections
The olfactory bulb is located in the forebrain and is responsible for interpreting smell signals, while the locus ceruleus in the brainstem supports its function through long nerve fibers.
The study included evidence from both mice and human subjects.
Researchers used brain tissue analysis and PET scanning to better understand how these early changes occur in the brain.
