In recent years, epigenetic clocks have gained prominence as biomarkers for assessing biological age. However, the biological mechanisms underlying these clocks remain poorly understood. This study, published in Genome Medicine, investigates the role of blood cell composition in influencing DNA methylation age and age acceleration, providing new insights into their biological interpretations.
What this study does not show
This study does not establish a direct causal relationship between blood cell composition and health outcomes, nor does it imply that alterations in blood cell composition can be used to modify biological age or health risks.
The researchers began by developing a principal component analysis (PCA) method that effectively addresses the collinearity issues present in blood cell counts. This innovative approach allowed for a more nuanced understanding of how different blood cell types contribute to the estimation of DNA methylation age and age acceleration.
Utilizing a substantial dataset of 4,058 samples, the study quantified the contribution of various blood cell compositions to DNA methylation age, revealing that up to 53% of the variation in DNA methylation age can be attributed to cell counts. Notably, the balance between naïve and memory T cells was identified as a significant contributor to this variation.
In addition to examining DNA methylation age, the researchers also analyzed the relationship between age acceleration and health outcomes. They investigated 176 incident health outcomes in a larger cohort of 18,859 individuals. The findings indicated that the associations between age acceleration and cell counts were weaker, explaining up to 21% of the variance, with neutrophils playing a primary role in the second-generation epigenetic clocks.
Interestingly, the study found that blood cell composition significantly attenuates the association between age acceleration and health outcomes, although the effect was described as modest. This suggests that while blood cell composition influences the biological interpretation of age acceleration, its contribution to mortality and disease outcomes is limited.
Overall, the results indicate that DNA methylation age and age acceleration reflect different biological processes, with distinct associations to blood cell composition. The study emphasizes the complexity of biological aging and the need for further research to unravel the underlying mechanisms.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Not established
- Clinical utility: Not established
The evidence is based on primary research in human subjects.