What can a handshake tell about you? Culturally, different things. In some places, it indicates confidence, in others, aggression or weakness.

Demographers at the International Institute for Applied Systems Analysis say it can show the rates of aging among different population groups.

In a PLOS ONE paper, IIASA researcher Serguei Scherbov and Warren Sanderson of Stony Brook University did a review of over 50 published studies that focus on people of all ages around the world. Since the measure is already commonly used, data are readily available.  They also claim that hand grip corresponds to other markers of aging such as people's future mortality, disability, cognitive decline, and ability to recover from hospital stays.  

What can it tell us? Their credit card cleared.

"Hand-grip strength is easily measured and data on hand-grip strength now can be found in many of the most important surveys on aging worldwide," says Sanderson.

They say they study also demonstrates how such a test could be used as a measure for aging to compare different population groups. The study used data from one such survey, the United States Health and Retirement Survey (HRS), to show how this could be done.

Click image for larger size. People with the same hand-grip strength based age, by age, gender, race, and education, means and 95% confidence intervals.  doi:10.1371/journal.pone.0096289

Scherbov says, "We found that based on this survey, a 65-year-old white women who had not completed secondary education has the same handgrip strength as a 69-year-old white women who had completed secondary education. This suggests that according to a handgrip strength characteristic their ages are equivalent and 65 year-old women ages 4 years faster due to lower education attainment."

Previous research by Sanderson and Scherbov said that measuring age simply by the number of years people have lived does not measure variations in the aging process correctly. Using new characteristic-based approaches such as the one in this paper, using a physical test like hand-grip, the researchers can identify differences in the aging process between population groups that may not otherwise become apparent. 

Scherbov says, "Our goal is to measure how fast different groups in a society age. If some group is getting older faster than another, we can ask why that might be and see whether there are any policies that could help the faster aging group."