The Horvath, Hannum and skin and blood (SB) clocks are widely used because of their ability to robustly predict either the chronological age of unknown donors or biological age discrepancies in various tissues in a single individual. To date, multiple DNAmAge clocks have been developed, with some variation in composition and outcome ( Table 1). Positive DNAmAA (biological age is projected to be older than chronological age) has been associated with diabetes, cancer, cardiovascular disease and all-cause mortality, although causality still has to be established. Residuals from the regression of epigenetic age on chronological age are defined as DNAm age acceleration (AA, DNAmAA). These predictors are termed ‘epigenetic clocks’ and quantify (in years) a biological age estimate. DNAm levels at specific CpG sites (referred to as clock CpGs) can also be used to predict chronological age. DNAm changes accumulate with age and are thought to mediate the effects of environmental risk factors on disease. ĭNA methylation (DNAm) refers to attachment of a methyl group to a DNA base. Ultimately, the availability of such markers could allow for improved targeted intervention through the identification of high-risk, functionally declining individuals before clinical symptoms appear. For this reason, extensive efforts have been made to develop markers that are able to reflect biological aging better than years since birth do. A group of peers, for example, may be the same chronological age, yet exhibit a spectrum of age-related deterioration. Although easily accessible and standardized, chronological age as a biomarker is limited by its inability to portray changes in biological functionality accurately over the life span, especially in later life. Chronological age is an integral component of frailty, noncommunicable disease risk and mortality. ![]() It is essential to continue studying under-represented population groups to ensure methylation-derived indicators are robust and useful in all populations.Īs global life expectancy continues to increase, the chronic disease burden expands and the need for a better understanding of how to promote healthy aging is emphasized. Conclusions: Each clock provides a different fraction of information regarding the aging body. GrimAge more accurately characterizes biological decline in this African cohort compared with PhenoAge owing to the unique inclusion of smoking-related damage in the GrimAge estimate. Results: The results confirm the tendency of DNA methylation clocks to underestimate the biological age of older individuals. Methods: The age estimation accuracy of the Horvath, Hannum and skin and blood clocks and the relative age-related mortality risk and predicted time to death portrayed by the PhenoAge and GrimAge biomarkers are investigated, respectively. This manuscript characterizes the behavior of five DNA methylation clocks in 120 older Black South African men. Aims: DNA methylation clocks are widely used to estimate biological age, although limited data are available on non-European ethnicities.
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