A new way to measure how humans age suggests that Latinos withstand life's wear and tear better than non-Latino Caucasians.

A new way to measure how humans age suggests that Latinos withstand life’s wear and tear better than non-Latino Caucasians, and that they may have their Native American ancestors to thank for their longer lives.

The new findings offer some insight into a long-standing demographic mystery: that despite having higher rates of inflammation and such chronic diseases as obesity and diabetes, Latinos in the United States have a longer average life span than do non-Latino whites.

Those findings emerge from an intriguing effort to devise a biological clock — a standard measure of age more revealing than birthdays, walking speed, wrinkled skin or twinkly eyes. By doing so, researchers hope to glean why some people die young while others live long, to understand what chronic diseases have to do with aging, and to predict and increase patients’ life spans. A reliable measure of biological age could also set a standard by which to judge the effectiveness of anti-aging therapies.

At the University of California, Los Angeles, bioinformatician Steve Horvath has devised a measure of aging that reflects the activity level of the epigenome, the set of signals that prompts an individual’s genes to change their function across the life span in response to new demands.

Horvath’s “epigenetic clock” captures a key feature of aging: that as we grow older, there are complex but predictable changes in the rate at which our genes are switched on and off by a chemical process called DNA methylation. To arrive at a single measure of a person’s biological age and then compute his or her speed of aging, Horvath has proposed to measure epigenetic activity at 353 sites in a person’s genome.

Earlier efforts to devise an epigenetic clock suggested that biological age, and the speed of aging, not only differ among populations and from person to person: The tissues in each of us may age at different rates. That may explain, for instance, why some organs and tissues are more vulnerable than others to such age-related diseases as cancer.

The new study, published this week in the journal Genome Biology, set out to refine and test that clock. To do so, Horvath and his colleagues analyzed blood, saliva and lymphoblastoid samples collected from 5,162 participants in a wide range of studies.

Those participants included not only black, white and Latino Americans but also Han Chinese, members of the Tsimane Amerindian tribe in South America, and two separate groups of Central Africans: rain-forest-dwelling hunter-gatherers and agrarians living in grasslands and open savannas.