Adult hippocampal neurogenesis is abundant in neurologically healthy subjects and drops sharply in patients with Alzheimer's disease.
Level 4 - case-series / case-control
Cross-sectional post-mortem comparative study of human brain tissue (healthy vs. Alzheimer's disease).
PubMed 30911133 · doi:10.1038/s41591-019-0375-9
What was done
Researchers analyzed post-mortem human brain tissue from neurologically healthy subjects (up to the ninth decade of life) and individuals diagnosed with Alzheimer's disease (AD). Using tightly controlled sample collection and tissue processing techniques, they assessed the presence, quantity, and differentiation stages of immature neurons in the dentate gyrus.
What was found
The abstract reports that thousands of immature neurons displaying varying degrees of maturation were identified in the dentate gyrus of neurologically healthy subjects up to their 90s. In contrast, both the number and maturation level of these immature neurons progressively declined as AD advanced. No exact sample sizes, numerical counts, or statistical values are reported in the abstract.
Why it matters
These findings indicate that adult hippocampal neurogenesis persists throughout healthy human aging and suggest that its reduction may be an underlying mechanism of memory deficits in Alzheimer's disease.
Limits
The abstract does not provide the total sample size (n), post-mortem delay intervals, or detailed patient characteristics. As a post-mortem observational study, it demonstrates anatomical correlation rather than direct mechanistic causation in living humans.