Patterns of DNA methylation, a type of epigenetic marker that regulates protein production, have been shown to change with age in fairly well defined ways. This provides the basis for a biomarker of aging, a way to quickly measure how physically aged an individual is, meaning how much age-related cell and tissue damage he or she has accumulated in comparison to peers of the same chronological age. A part of the process of validating this approach to measuring biological rather than chronological age is to compare age-related disease incidence over time in people with higher and lower measures of biological age:

A person's epigenetic age is calculated based on an algorithm measuring 71 blood DNA methylation markers that could be modified by a person's environment, including environmental chemicals, obesity, exercise and diet. This test is not commercially available but is currently being studied by academic researchers. In DNA methylation, a cluster of molecules attaches to a gene and makes the gene more or less receptive to biochemical signals from the body. The gene itself - your DNA code - does not change. This is the first study to link the discrepancy between epigenetic age and chronological age with both cancer development and cancer death using multiple blood samples collected over time. The multiple samples, which showed changing epigenetic age, allowed for more precise measurements of epigenetic age and its relationship to cancer risk. Other studies have looked at blood samples collected only at a single time point.

The study was a longitudinal design with multiple blood samples collected from 1999 to 2013. Scientists used 834 blood samples collected from 442 participants who were free of cancer at the time of the blood draw. For each one-year increase in the discrepancy between chronological and epigenetic ages, there was a 6 percent increased risk of getting cancer within three years and a 17 percent increased risk of cancer death within five years. Those who will develop cancer have an epigenetic age about six months older than their chronological age; those who will die of cancer are about 2.2 years older, the study found.