Compare methods

	Epigenetic Clock (DNA Methylation Age)	Fried Frailty Phenotype
Field	Social Gerontology	Social Gerontology
Family	Regression model	Process / pipeline
Year of origin	2013	2001
Originator	Steve Horvath	Linda P. Fried and the Cardiovascular Health Study Collaborative Research Group
Type	Penalized-regression predictor of age from DNA methylation	Operational phenotype for physical frailty in older adults
Seminal source	Horvath, S. (2013). DNA methylation age of human tissues and cell types. Genome Biology, 14(10), R115.	Fried, L. P., Tangen, C. M., Walston, J., Newman, A. B., Hirsch, C., Gottdiener, J., ... & McBurnie, M. A. (2001). Frailty in older adults: evidence for a phenotype. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 56(3), M146-M157.
Aliases	DNAm Age, Horvath Clock, DNA Methylation Clock, Methylation Age Predictor	Physical Frailty Phenotype, CHS Frailty Criteria, Fried Criteria, Phenotypic Frailty
Related	4	4
Summary	An epigenetic clock is a statistical predictor that estimates age from patterns of DNA methylation, the chemical marks on the genome that change in a regular way over the life course. The most influential is Steve Horvath's 2013 multi-tissue clock, which predicts chronological age from methylation levels at 353 specific CpG sites using a penalized regression model. Methylation is measured as a beta-value between zero and one at each site, representing the fraction of cells in which that site is methylated, and the clock combines a weighted set of these values into a predicted DNA methylation age, or DNAm age. Remarkably, Horvath's clock works across many tissues and cell types from the same individual, suggesting it captures a fundamental aging process rather than a tissue-specific quirk. The difference between predicted DNAm age and actual chronological age, known as epigenetic age acceleration, serves as a biomarker of biological aging. Age acceleration predicts mortality and a range of age-related conditions, which has made epigenetic clocks central to modern aging research.	The Fried frailty phenotype operationalizes frailty as a distinct biological syndrome of physical decline rather than as disease or disability. Introduced by Linda Fried and the Cardiovascular Health Study Collaborative Research Group in 2001, it defines frailty through five measurable criteria — unintentional weight loss, self-reported exhaustion, low physical activity, slow gait speed, and weak grip strength — and classifies older adults as robust, pre-frail, or frail by counting how many criteria are present. The phenotype gave gerontology a reproducible, predictive measure of vulnerability that forecasts falls, disability, hospitalization, and mortality, and it remains one of the two dominant operationalizations of frailty alongside the deficit-accumulation index.