Epigenetic age, a key marker for measuring biological aging, fluctuates throughout the day, according to a recent study. 

Published in the journal Aging Cell, the study adds a new dimension to the understanding and measurement of biological aging.

Researchers used 17 different epigenetic clocks, which assessed aging through DNA methylation patterns, to track age predictions over a 24-hour cycle. They noted fluctuations in age predictions, with the highest estimates at noon and the lowest around midnight. This indicated that the time of day when blood samples are collected can impact the estimated biological age.

The study linked these fluctuations to the daily variations in the composition of white blood cells, particularly neutrophils, which follow a 24-hour rhythm. Even with adjustments for these variations, the timing of DNA methylation continued to influence age predictions significantly.

Analyses were performed on samples collected every 3 hours over a 3-day period from a 52-year-old male, enabling detailed monitoring of temporal changes. This approach showed that epigenetic clocks, particularly those estimating mitotic age, were most affected by time-of-day variations.

The study highlighted the influence of sample collection timing on age estimation in research and clinical settings. The researchers noted that recognizing these fluctuations is essential to accurately interpret biological age, which can affect studies on aging, disease prognosis, and the assessment of lifestyle interventions aimed at modifying biological age.

The results suggest that incorporating daily rhythms into the calculation of biological age could improve the accuracy and reproducibility of aging research, they noted.

The authors declared no conflicts of interests.