Study links nerve damage to Alzheimer's and loss of smell
Losing your sense of smell can actually be one of the first signs of Alzheimer's—and it turns out, this is caused by immune cells in the brain attacking nerve fibers, not by damage to your nose itself.
Researchers in Germany found that these nerve fibers (linking a region called the locus coeruleus to the olfactory bulb) start breaking down before any memory problems show up.
Immune cells in the brain attack nerve fibers
Using mice with early-stage Alzheimer's, scientists discovered that immune cells called microglia target and remove these nerve connections after picking up certain "eat me" signals. This interrupts normal smell processing.
When researchers checked human brains and PET scans from real patients, they saw similar nerve loss and immune activity—confirming it happens in people too.
Early diagnosis and treatment could make a big difference
Spotting changes in your sense of smell could help doctors catch Alzheimer's much earlier—maybe even before memory loss starts.
The findings suggest that future therapies could target early immune dysfunction to protect brain function.
Early diagnosis might also make current therapies work better for those at risk.