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. Why is that?
A new method of measuring how humans age suggests that Latinos withstand life’s wear and tear better than non-Latino Caucasians, and their Native American ancestors may be the reason.
These 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. Researchers involved in the effort hope to learn why some people die young while others live long, to understand what chronic diseases have to do with aging, and to predict and increase life spans.
UCLA bioinformatician Steve Horvath has devised a measure of aging that reflects the activity level of the epigenome, the set of signals that prompts one’s genes to change their function across the life span as demands arise.
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 biological age and then compute a person’s speed of aging, Horvath has proposed to measure epigenetic activity at 353 sites in the individual’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 also age at different rates. That may explain, for instance, why some organs and tissues are more vulnerable than others to age-related diseases such as cancer.
To refine and test that clock, Horvath and colleagues analyzed blood, saliva and other samples collected from 5,162 participants in a wide range of studies.
Those participants included not only blacks, whites and Latinos from the United States 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.
The Tsimane, an indigenous people who forage and cultivate crops in the lowlands of Bolivia, offer an especially good test of the epigenetic clock: Constantly bombarded with bacterial, viral and parasitic infections, the Tsimane typically experience high rates of inflammation, which has widely been seen as a marker for aging. But they rarely show risk factors for heart disease or develop Type 2 diabetes as they age, and obesity, hypertension and unhealthy cholesterol are virtually nonexistent.
The epigenetic clock found that the Tsimane aged even more slowly than Latinos.
But that finding came despite strong evidence that, after age 35, a Tsimane’s immune system was close to exhausted and inflammation levels “make him look like a 90-year-old,” Horvath said.
“This result sheds light on what is frequently called the Hispanic paradox,” he said. “It suggests that what gives Hispanics their advantage is really their Native American ancestry, because they share ancestry with these indigenous Americans.”
Horvath noted that Latinos’ slower aging rate cannot be explained by lifestyle factors such as diet, socioeconomic status, education or obesity, because researchers adjusted for such factors.
The study may also shed light on a different demographic oddity: that once African Americans have reached 85, they tend to live longer than whites of the same age. Using a new gauge of biological aging, the researchers found that older African Americans age more slowly than do Caucasians of the same chronological age.