Some people carry one of the strongest genetic risk factors for Alzheimer's disease yet never develop it, remaining mentally sharp well into their 80s. For years, scientists have wondered what protects these individuals despite their increased genetic vulnerability.

Now, researchers at Columbia University have uncovered a biological mechanism that could help explain this remarkable resistance. Their findings point to a rare genetic mutation that protects the brain's blood vessels from damage, potentially opening a new path toward Alzheimer's treatments.

The discovery builds on research the team published two years ago involving APOE ε4, a gene variant strongly associated with Alzheimer's risk. The scientists found that some people carrying APOE ε4 also possess a rare protective mutation in the fibronectin (FN1) gene.

Fibronectin is a protein that helps support the structure of tissues.…