Telomere tests: How well do they predict biological age
You may have heard about at-home DNA testing and might have even sent a cheek swab or saliva sample off in the mail to learn more about your ancestry or disease risk. Now, a growing number of companies are offering over-the-counter tests to measure your telomeres and provide insights into how your body is aging.
What are telomeres?
Telomeres are combinations of DNA and protein at the end of a chromosome. Similar to plastic tips on the ends of shoelaces, telomeres prevent DNA from “fraying” or losing genetic material. Your telomeres get shorter as you get older.
“Telomeres are the main biomarkers of aging,” says Juan Luis Sánchez González PhD, professor of nursing and physiotherap at the University of Salamanca in Spain. “They are considered to be the clocks or timers of the cell since they mark the number of cell divisions until the cell dies.”
Some research has linked shorter telomere length to an increased risk of diabetes, cardiovascular disease and shorter lifespan. Research has also focused on changing telomere length as an avenue to prevent age-specific disease risk and limit the impacts of aging.
The impact of telomere length and cognitive performance or dementia risk is less clear.
In a 2022 study, González compared telomere length of physically active women in their seventies with inactive women in the same age group and found no correlation between telomere length and cognitive performance. Separate research found shorter and longer telomere length were associated with an increased risk of Alzheimer’s disease. One researcher noted the link was “inconsistent.”
“This is a new field,” says Sue Rutherford Siegel Ph.D., a genetic researcher and professor in the Biomarker Core Lab at Penn State. “We’re still trying to research and identify all the ramifications of telomere shortening at this point in time.”
Does telomere testing work?
Some companies that offer at-home testing promise your DNA will reveal your true biological age and provide insight into your cellular health. In reality, the results obtained through telomere testing might not be valuable.
“It’s not like a person who has [a certain] measurement of telomere length is in good health because there’s a great range [in normal telomere length],” says Siegel. “Telomeres will shorten with age naturally…it’s just the natural progression of aging, but even among 60-year-olds, you’ll find a vast amount of differences between those that have long and short [telomeres].”
Not only is there no standard for what constitutes a “healthy” telomere length by age, there are also multiple methods for evaluating telomere length and often significant variations in the results. Research shows that one common test, the quantitative polymerase chain reaction or qPCR test, has up to a 20% variability in results and testing on different days can lead to different results.
“Some of it is measurement error but some [changes to telomere length] may be true biological regulation [or] periods of shortening and compensatory periods of lengthening,” says Elissa Epel PhD, co-director of the Aging, Metabolism and Emotions Center at the University of California. “Having short telomeres is simply a risk factor for health [but] it only slightly increases your risk for disease. So many other factors go into your risk [like] your health behaviors and your genetics.”
Given the challenges, Epel doesn’t believe it’s worth investing in at-home telomere testing, adding, “If someone is dedicated to getting repeated measures of telomere length, before, during and after a big lifestyle change, that could be interesting. But for me [testing] is not a priority.”
How to preserve telomere length
It might not be necessary to hand over your credit card information to learn your telomere length but it is important to prioritize healthy habits that could preserve or improve telomere length.
Eating a diet chock full of legumes, nuts, fruits, and coffee (and skipping sugar-sweetened drinks, red and processed meats) could help preserve telomere length; exercise, optimal sleep and quitting (or not smoking) were also linked to less telomere shortening—but Siegel notes that these are the oft-cited hallmarks of a healthy lifestyle and beneficial regardless of their impact on telomeres.
Despite a growing body of evidence, even researchers admit that further studies are needed to get a better understanding of the connection between telomere length and healthy aging.
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