In the realm of longevity research, epigenetic clocks have emerged as key biomarkers for assessing biological age. However, the underlying biological mechanisms that drive 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.
Background
Previous research has indicated that the proportions of naïve and memory T cells can significantly affect epigenetic clocks. The authors of this study aimed to delve deeper into this relationship, particularly focusing on how blood cell composition might serve as a driver of variations in DNA methylation age.
Methods
The researchers developed a principal component analysis (PCA) method that addresses the collinearity of blood cell counts, allowing for a more nuanced understanding of how these counts contribute to epigenetic measurements. They analyzed a substantial dataset comprising 4,058 samples to quantify the impact of cell composition on DNA methylation age and age acceleration, estimated by various epigenetic clocks.
Furthermore, the study examined the influence of blood cell composition on the association between age acceleration and 176 incident health outcomes in a larger cohort of 18,859 individuals.
Results
The findings revealed that up to 53% of the variation in DNA methylation age could be attributed to blood cell counts, with a notable contribution from the balance of naïve and memory T cells. In contrast, the associations between age acceleration and cell counts were weaker, explaining up to 21% of the variance, particularly for 2nd-generation clocks, which were mainly influenced by neutrophil counts.
Additionally, the study validated the role of cell composition in epigenetic clocks through experiments involving artificial cell mixtures. Importantly, the analysis indicated that cell composition significantly attenuates the association between age acceleration and various health outcomes, although this effect was described as modest.
Conclusions
The study concludes that DNA methylation age (DNAmAge) and age acceleration (AgeAccel) exhibit markedly different associations with blood cell composition, suggesting they reflect distinct biological processes. Notably, the contribution of blood cell composition to age acceleration’s association with mortality and incident disease outcomes was found to be minor.
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 provide evidence for specific interventions based on these findings.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Partial
- Clinical utility: Not established
The evidence is based on primary research involving human subjects.