# CD34+ Hematopoietic Stem Cell Counts in Alzheimer’s Disease: A Meta-Analysis

## TL;DR

This study finds that Alzheimer's patients may have higher levels of CD34+ stem cells in their blood, but the results are not conclusive due to inconsistencies among studies.

## Contribution

The paper provides a meta-analysis comparing CD34+ stem cell counts in Alzheimer’s patients versus controls, revealing potential differences but highlighting significant heterogeneity.

## Key findings

- AD patients showed increased CD34+ cell counts compared to controls in a common effects model.
- Significant heterogeneity (I2 = 87.1%) was observed among the included studies.
- Random effects model results were non-significant, suggesting variability in study outcomes.

## Abstract

Purpose: To assess the presence and quantity of CD34+ hematopoietic stem cells in patients with Alzheimer’s disease (AD) through a meta-analysis. Methods: A systematic search of the databases identified the observational and interventional studies reporting baseline CD34+ cell counts in AD patients. The data on mean counts and the measures of variation were extracted. Standardized mean differences (SMDs) were calculated using common and random effects models to compare the CD34+ cell counts between the AD patients and controls. Heterogeneity among the studies was evaluated using tau2, tau, and I2 statistics. The risk of bias was assessed using the Newcastle–Ottawa Scale and the ROBINS-I tool. Patients: Five studies were included, comprising four observational studies and one open-label trial, with a total of 271 participants (139 AD patients and 132 controls). Results: The meta-analysis indicated an increase in CD34+ cell counts of the AD patients when compared to the controls. The common effects model showed a moderate SMD of 0.2964 (95% CI:0.0490–0.5437). However, the random effects model yielded a non-significant SMD of 0.2326 (95% CI: −0.4832–0.9484). Significant heterogeneity was observed among the studies (I2 = 87.1%, p < 0.0001). Conclusion: AD patients may exhibit higher circulating CD34+ cell counts than the controls, but substantial heterogeneity and potential biases limit definitive conclusions.