Many chronological aging clocks can be found throughout the epigenome: Implications for quantifying biological aging

Area of Science:

• Epigenetics and computational biology
• Gerontology and aging research

Background:

• Epigenetic alterations are key features of aging and age-related diseases.
• DNA methylation patterns are used to develop computational
• epigenetic clocks
• to estimate biological age.
• Understanding the link between clock sites and aging mechanisms is crucial.

Purpose of the Study:

• To investigate the relationship between predictive sites in epigenetic clocks and the underlying biology of aging.
• To assess the performance of tissue-specific versus pan-tissue epigenetic clocks.
• To evaluate the utility of current epigenetic clocks for understanding aging and disease.

Main Methods:

• Analysis of over 450,000 DNA methylation sites across 9,699 samples.
• Development and comparison of various epigenetic clocks.
• Assessment of clock performance against telomere length and disease association.

Main Results:

• Approximately 20% of measured cytosines can form epigenetic clocks outperforming telomere length in age prediction.
• Predictive sites showed minimal average methylation change (~1.5%) and were underrepresented in regulatory regions.
• Weak associations were found between accelerated epigenetic aging and disease.
• Tissue-specific clocks showed varying performance compared to pan-tissue clocks.

Conclusions:

• While epigenetic clocks accurately predict chronological age, their current design may have limited utility for understanding aging biology or as surrogate endpoints for anti-aging interventions.
• Purpose-built clocks for specific tissues, age ranges, or phenotypes might offer improved performance for targeted applications.
• The necessity of purpose-built clocks warrants a re-evaluation of the broader utility and application of epigenetic clocks in aging research.