Chronological and Cellular Age Don't Always Match

If you exercise regularly, refrain from smoking, and have scored in the genetic lottery, then you may be able to truthfully shave a few years off your age. Researchers from the University of North Carolina’s Lineberger Comprehensive Cancer Center have now found a way to calculate cellular aging, as they reported in a study that will be published in the journal, Aging Cell.

Five years ago, these same researchers discovered that as cells and tissue age, the expression of a certain protein--p16INK4a--dramatically increases in most mammalian organs. Now they have proven that p16INK4a is present in human blood, and they’ve paved the way toward creating a simple blood test to measure a person’s molecular—as opposed to just chronological—age.

In their study, the researchers tested the blood of 170 healthy volunteers, who also filled out a questionnaire about current and past health status and health behaviors. They found that the expression of the biomarker strongly correlated with the donor’s chronological age and, in fact, increased exponentially with age. In addition, increased levels were independently associated with tobacco use.

Norman Sharpless, M.D., the senior author of the study, wasn’t surprised to find that cigarette smoking accelerates cellular aging. “What did surprise us, was the very beneficial effect of exercise. It makes you molecularly younger.” And despite other studies that suggest calorie restriction slows aging, “We found a very weak correlation between the biomarker and obesity,” said Dr. Sharpless, who is also an associate professor of medicine and genetics at UNC’s School of Medicine.

“Although we don’t know whether this test is a good reflection of cellular age in all types of human tissues, we believe it is a first step toward a better understanding of issues like the suitability of organs for transplantation, how well patients are likely to recover after surgery or the future toxicity of chemotherapy for cancer patients.”

But, Dr. Sharpless cautioned, the widespread application of this test could have its drawbacks. While you may want to know if your cellular and chronological ages match, you may not want those results shared with your employer or health insurance company.