In the realm of epigenetics, DNA methylation age has emerged as a significant biomarker for biological aging. However, the biological mechanisms underlying these epigenetic clocks remain poorly understood. This study, published in Genome Medicine, investigates the role of blood cell composition in interpreting DNA methylation age and age acceleration.
What this study does not show
While the study identifies the influence of blood cell composition on DNA methylation age, it does not establish a direct causal relationship between these factors and specific health outcomes.
The researchers developed a principal component analysis (PCA) method to address the challenges posed by collinearity in blood cell counts. This innovative approach allowed them to quantify the contribution of different blood cell types to DNA methylation age and age acceleration across a sample of 4,058 individuals.
Findings revealed that up to 53% of the variation in DNA methylation age can be attributed to the proportions of various blood cell types, particularly the balance between naïve and memory T cells. In contrast, the influence of cell composition on age acceleration was found to be weaker, explaining up to 21% of the variance, with neutrophils being the primary contributors in 2nd-generation epigenetic clocks.
Moreover, the study examined the relationship between age acceleration and 176 incident health outcomes in a larger cohort of 18,859 individuals. It was found that blood cell composition significantly attenuates the association between age acceleration and these health outcomes, although the effect was described as modest.
In conclusion, the study highlights that DNA methylation age (DNAmAge) and age acceleration (AgeAccel) reflect different biological processes, influenced distinctly by blood cell composition. Despite the substantial contribution of cell types to the variation in DNA methylation age, their role in the association with mortality and disease outcomes appears limited.
Evidence scorecard
- Analytic validity: established
- Clinical validity: not established
- Clinical utility: not established
The evidence is based on primary research involving human subjects.