Previously, researchers haveidentified a key protein, called p16INK4a, that increase in mammalian organs as as cells and tissues age. Recently, they have found out that the protein is also present in human blood and is strongly correlated both with chronological age and with certain behaviors such as tobacco use and physical inactivity, which are known to accelerate the aging process. Based on these findings, they have developed a simple blood test to detect p16p16INK4a expression, which is present in cells called T-lymphocytes, also known as T-cells.

They found that expression of the biomarker was 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 and physical inactivity as well as with biomarkers of human frailty.

Sharpless said that the researchers were surprised by some of their findings, "We found a very weak correlation between the biomarker and obesity - as measured by body mass index (BMI) - despite other data suggesting that caloric restriction slows aging. The data suggest the possibility that reduced exercise may actually be worse with regard to molecular age than a higher BMI."

"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," he added.

The study has been published online ahead of print in the journal Aging Cell.

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