"Why Your Birth Date May Not Match Your Body's Age"

"In the study, researchers looked at a group of people, all of whom were 38 years old. The researchers determined these participants' "biological ages" based on how well their body systems were working. To determine each person's biological age, the researchers looked at the participants' cognitive abilities, blood pressure and markers of their kidney, liver, lung and immune system function, among other measures.

They found that the participants' biological ages ranged from 28 to 61. In other words, some of the 38-year-olds functioned as well as people in their late 20s, whereas others more closely resembled the functioning of people in their early 60s...

The same information that the researchers used in the study to determine people's biological ages is typically collected during routine medical checkups. Doctors could use this data to explain to patients, in a relatable way, how their lifestyles are affecting their health, Belsky said."
http://m.livescience.com/51506-aging-in-young-people.html?cmpid=514627_20150710_48925016&adbid=10152864154596761&adbpl=fb&adbpr=30478646760