Epigenetic clocks use patterns of DNA methylation that correlate with age. Numerous studies have shown that people with epigenetic age higher than chronological age have a raised risk of disease. This works the other way as well; patient populations with a range of age-related diseases tend to have higher epigenetic age measures than their healthier peers of the same chronological age. The study noted here is the most recent in a growing body of evidence to suggest that epigenetic clocks measure something potentially useful about aging.
What exactly it is about aging that epigenetic clocks measure is still an open question, however. The patterns of DNA methylation were discovered by analysis of epigenetic data by age, not built from an understanding of the underlying processes. It is quite possible that they reflect only a fraction of the important processes in aging, which is fine when aging proceeds in a unified way, all processes roughly aligned with one another, but the utility of such clocks will end when it becomes possible to address any one specific process of aging via rejuvenation therapies. Take clearance of senescent cells, for example: at this point no-one has the first idea as to what that will do to epigenetic clock measures, and until data is established the clocks aren't all that helpful for developers working on senolytic therapies to selectively destroy senescent cells.
Scientists speculate that biologic age may be tied to environmental exposures. If so, it may be a useful indicator of disease risk. They used three different measures, called epigenetic clocks, to estimate biologic age. These clocks measure methylation found at specific locations in DNA. Researchers use these clocks to estimate biologic age, which can then be compared to chronologic age. The researchers used DNA from blood samples provided by women enrolled in the Sister Study, a group of more than 50,000 women in the U.S. and Puerto Rico. The study was specifically designed to identify environmental and genetic risk factors for breast cancer. The research team measured methylation in a subset of 2,764 women, all of whom were cancer-free at the time of blood collection.
"We found that if your biologic age is older than your chronologic age, your breast cancer risk is increased. The converse was also true. If your biologic age is younger than your chronologic age, you may have decreased risk of developing breast cancer. However, we don't yet know how exposures and lifestyle factors may affect biologic age or whether this process can be reversed. If you look at a group of people who are all the same age, some may be perfectly healthy while others are not. That variability in health may be better captured by biologic age than chronologic age."