Surprising race- and gender-based differences in telomeres—the chains of repeating molecules that protect the ends of chromosomes from damage—show that the structures’ relationship to age and health outcomes is more complex than originally thought, according to a USC-led study.
In the search for a reliable aging biomarker, or a way to directly measure how an individual is physiologically or biologically aging, much attention has been focused on telomeres, said Lauren Brown, PhD in Gerontology candidate at the USC Leonard Davis School of Gerontology. She explained that some aging researchers first thought that telomeres might be a single, all-encompassing indicator of aging, with the chains getting shorter over time and in response to environmental or social stressors.
“We wanted to know if this really was a valid measure of aging at the population level that took into account social or environmental factors that might speed up the aging process,” she said, “or if differences in telomere length improved our understanding of the pervasive problem of racial and ethnic health disparities.”
Brown authored an article examining the differences in telomere length between older adults of different genders and races, which was published online in the Journal of Aging and Health in July 2016, and presented her research at the Gerontological Society of America’s Annual Scientific Meeting in November 2016. The study used information from the 2008 U.S. Health and Retirement Study and included data from more than 5000 white, black and Hispanic adults over age 54.
Longer telomere length has been thought to reflect better health and a younger biological age, but the analysis yielded surprising findings. Brown and colleagues found that white older adults had the shortest telomeres on average while black older adults had the longest. Thus, telomere length itself didn’t seem to explain racial or ethnic disparities in aging, since white populations had shorter telomeres yet have longer average lifespans and better health outcomes relative to black populations, even after controlling for socioeconomic factors and education, Brown said.
The findings indicate that telomere length itself isn’t the powerful all-encapsulating aging biomarker that researchers once hypothesized it was, Brown said.
In a follow-up study, “telomere length itself didn’t appear to be a good predictor for health outcomes, especially in people of color,” she said. “[Shorter telomeres] might be a better indicator of aging in white populations but aren’t necessarily the end-all-be-all indicator of biological age across diverse populations of older adults.”
However, she added that she hopes to further examine telomeres, including how they change over time, and their relationship to health outcomes. One possible explanation for the findings might be that while black and Hispanic individuals may have longer telomeres on average across the life course, their rate of telomere shortening could be greater than that of whites, reflecting accelerated aging and worse health outcomes associated with minority populations.
“Once we obtain longitudinal data, we can see if people of color are starting with longer telomeres but experiencing faster telomere shortening,” Brown said. “Faster shortening could be a factor in aging-related health outcomes as well as a symptom of environment and social stresses that characterize the lives of people of color and contribute to accelerated aging.”
At the 2016 GSA Meeting, Brown chaired and presented her telomere research during a symposium, “How Do Biomarkers Inform Our Understanding of Race and Ethnic Differences in Health?” on the wider subject of applying biomarkers to health disparities between different populations. Within this symposium, Brown and colleagues made the argument that the recent emergence of biomarkers in longitudinal, nationally representative and diverse samples of older adults presents an opportunity to better characterize differences in health by race or ethnicity.
“It’s important that we understand what we are measuring when we collect biomarkers of aging and that we are not just capturing the aging process in one group of people,” Brown said. “Good biomarkers of aging should advance our understanding of the aging process and recognize differences in health across racially and ethnically diverse populations.”
As researchers’ understanding of the complexities of telomere biology continue to deepen, in future analyses Brown plans to use genetic ancestry to account for this potential heritability difference in telomere length that may be contributing to these surprising race/ethnic differences in telomere length in older ages. This may also help better isolate the social or environmental factors that cause accelerated aging and faster telomere shortening that would be expected among racially and ethnically diverse populations, she said.
Meanwhile, researchers are still on the hunt for a single biomarker of aging that is a better marker of the aging process than chronological age and can identify individuals at increased risk of disease, disability, and accelerated aging in late life.
“For now, the hunt continues, since absolute telomere length has proven not to be a consistent measure of age-related declines among racially and ethnically diverse older adults,” Brown said.
“One of the real pleasures of working with emerging scholars is that they often have a fresh take on longstanding challenges in research,” said USC Davis Assistant Professor Jennifer Ailshire, Brown’s mentor and co-author on the telomere studies. “Lauren’s work is helping us to think about whether and how biomarkers of aging can provide insights into enduring racial and ethnic disparities in health and aging.”