Scientists Discover the Brain May Enter a New Biological Phase Between 50 and 75

Single-cell and 3D genome analysis of the human hippocampus found a clear shift between roughly ages 50 and 75.

Microglia became more inflammatory and blood-like, while cells supporting the blood-brain barrier declined.

Genome organization also grew less stable across multiple cell types, suggesting brain aging is an active remodeling process, not just wear and tear.

The findings may help explain why aging sharply raises the risk of neurodegenerative diseases such as Alzheimer’s.