Researchers have used a new kind of biological clock to discover that Latinos age more slowly than any other ethnic group in the US.
The findings could lead to a greater understanding of the epigenetic changes – external factors influencing our DNA – that affect why all of us age differently, as well as solving a long-standing mystery over how Latinos enjoy such longevity in the face of greater susceptibility to certain health issues.
"Latinos live longer than Caucasians, despite experiencing higher rates of diabetes and other diseases. Scientists refer to this as the 'Hispanic paradox,'" says geneticist and biostatistician Steve Horvath from UCLA. "Our study helps explain this by demonstrating that Latinos age more slowly at the molecular level."
Recent figures from the US Centres for Disease Control and Prevention show that Latinos in the US live three years longer on average than Caucasians, with a life expectancy of 82, compared with 79 for Caucasians.
And a study published in 2013 found that Latinos, despite higher rates of inflammation and chronic diseases like obesity, enjoy a 30 percent lower risk of death at all ages when compared to other ethnic groups.
To investigate the anomaly, Horvath's team examined data sets containing DNA samples from more than 5,000 people across seven different ethnicities, including Latinos, Caucasians, Africans, African-Americans, East Asians, and an indigenous people of lowland Bolivia called the Tsimane, who are genetically related to Latinos.
Using an epigenetic age-predicting system Horvath developed in 2013 – which tracks how a natural process called DNA methylation changes as we grow older – the researchers found that Latino bodies are biologically 'younger' than non-Latinos of the same age.
And the finding isn't impacted by lifestyle factors that could affect health and longevity, say the researchers, as they'd accounted for things such as diet, socioeconomic status, and education levels in their research.
One example given by the team describes how, after menopause, the epigenetic clock suggests that Latino women's bodies are actually 2.4 years younger in biological terms than non-Latino women of the same calendar age.
And it's this invisible physical youthfulness that the researchers think helps Latinos fight off chronic diseases comparatively better as they get older – at least to a significant extent when compared to non-Latinos.
"We suspect that Latinos' slower ageing rate helps neutralise their higher health risks, particularly those related to obesity and inflammation," says Horvath. "Our findings strongly suggest that genetic or environmental factors linked to ethnicity may influence how quickly a person ages and how long they live."
But while the study suggests that Latinos enjoy a significant biological advantage over other ethnic groups in the US, even they were outdone by the Tsimane – who age even more slowly.
According to the researchers' calculations, Latino blood on average is two years 'younger' than Caucasians of the same age, but Tsimane blood is two years younger still than the Latino blood.
The researchers think that both Latinos and the Tsimane can thank their common genetic ancestors for their ongoing biological youth.
"This result sheds light on what is frequently called the Hispanic paradox," Horvath told Melissa Healy at the Los Angeles Times. "It suggests that what gives Hispanics their advantage is really their Native American ancestry, because they share ancestry with these indigenous Americans."
The team also discovered that, across the ethnicities, men's blood and brain tissue age faster than women's, which they think could help explain why men have a shorter life expectancy than women.
Next the researchers intend to broaden their study, incorporating other kinds of human tissue into their analysis. The hope is that, at some stage in the future, these kinds of discoveries could slow down the process of ageing for everybody.
That kind of turning point may still be some way off, but it looks like we're getting closer.
The findings are reported in Genome Biology.