In recent years, epigenetic clocks have emerged as significant biomarkers for assessing biological age. However, the biological mechanisms underlying these clocks remain largely unclear. This study, published in Genome Medicine, investigates the role of blood cell composition in influencing DNA methylation age and age acceleration.
What this study does not show
This research does not establish a direct causal relationship between blood cell composition and health outcomes, nor does it provide definitive evidence on the clinical utility of epigenetic clocks in predicting health risks.
The authors conducted a comprehensive analysis involving 4,058 samples to quantify the impact of blood cell composition on DNA methylation age and age acceleration, as estimated by various epigenetic clocks. They developed a principal component analysis (PCA) method that effectively addresses the collinearity of blood cell counts, allowing for a more accurate interpretation of the data.
Key findings indicate that up to 53% of the variation in DNA methylation age can be attributed to cell counts, particularly highlighting the balance between naïve and memory T cells. In contrast, the association between age acceleration and cell counts explained a lesser degree of variance, up to 21%, with neutrophils playing a significant role in 2nd-generation clocks.
Furthermore, the study explored the influence of blood cell composition on the relationship between age acceleration and 176 incident health outcomes in a larger cohort of 18,859 individuals. The results suggest that while cell composition does attenuate the association between age acceleration and health outcomes, the effect is modest.
Interestingly, the findings reveal that DNA methylation age (DNAmAge) and age acceleration (AgeAccel) exhibit markedly different associations with blood cell composition, indicating that these metrics may reflect distinct biological processes. Despite the significant contributions of cell composition to epigenetic clocks, the variation attributed to blood cell composition has only a minor impact on associations with mortality and incident disease outcomes.
Overall, this study enhances our understanding of the biological interpretations of DNA methylation age and age acceleration, emphasizing the importance of considering blood cell composition in future research. However, further studies are needed to clarify the clinical implications of these findings.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Not established
- Clinical utility: Not established
The evidence is based on primary research involving human subjects.