A study published in the medical journal Genome Biology explains that all humans have a biological clock that measures the age of tissues.
The find may help scientists with cancer research and stem cell research as well as offer clues on how to slow the aging process.
According to a news release from UCLA, where the study's author Dr. Steve Horvath teaches genetics and biostatistics, the study found that some human tissue ages more quickly than others.
Via the news release:
While earlier biological clocks have been linked to saliva, hormones and telomeres, the new research is the first to result in the development of an age-predictive tool that uses a previously unknown time-keeping mechanism in the body to accurately gauge the age of diverse human organs, tissues and cell types.
The release goes on to explain that while working on the new tool, Horvath and his team discovered that "some parts of the anatomy, like a woman's breast tissue, age faster than the rest of the body." In other words, not all tissues' biological age (which measures the true state of an organism) matches its chronological age (years passes since birth).
Via the news release:
"Healthy breast tissue is about two to three years older than the rest of a woman's body," he said. "If a woman has breast cancer, the healthy tissue next to the tumor is an average of 12 years older than the rest of her body."
The results may explain why breast cancer is the most common cancer in women. Given that the clock ranked tumor tissue an average of 36 years older than healthy tissue, it could also explain why age is a major risk factor for many cancers in both genders.
Forbes explains that Horvath and his team "identified 353 DNA markers from 51 types of cells and tissue (including heart, lungs, brain, liver, cartilage, and kidney) that change throughout our lifetimes from before birth through old age."
Yahoo News spoke with Horvath about the significance of his findings.
"The big picture is really that people who study aging were really limited in that they weren't able to accurately measure age. It has been a long-standing hope to develop aging clocks that allow us to access the age of a cell or a tissue. The purpose being to learn why we age and what can be done against it."
Horvath said that his isn't the first aging clock, but his measures chemical changes to the DNA, which has made his epigenetic clock "far more accurate" than previous clocks. When he looked at 20 different types of cancer tissue, Horvath found that, on average, the cancerous tissue was "36 years older than one would expect based on chronological age. These results indicate that a tissue that looks much older than expected may be malignant."
"If we're really lucky, the epigenetic clock will guide the development of new treatments against aging and will allow us to develop treatments against aging," Horvath told Yahoo News. However, Horvath is cautious. "What I have not yet shown is that this epigenetic clock measures a process that causes aging. That's really the most pressing question."