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The Cutting Edge

Spit Take: You’re How Old?

SELF-CONSCIOUS ABOUT YROU AGE? Be careful where you spit because UCLA geneticists now can use saliva to reveal how old you are.

“Our approach supplies one answer to the enduring quest for reliable markers of aging,” says principal investigator Eric Vilain, M.D., professor of human genetics, pediatrics and urology. “With just a saliva sample, we can accurately predict a person’s age without knowing anything else about him or her.”

The findings were published in the online journal PLoS ONE.

Dr. Vilain and his colleagues looked at a process called methylation, a chemical modification of one of the four building blocks that make up our DNA. “While genes partly shape how our body ages, environmental influences also can change our DNA as we age,” Dr. Vilain says. “Methylation patterns shift as we grow older and contribute to agerelated disease.”

Using saliva samples contributed by 34 pairs of identical male twins between the ages of 21 and 55, UCLA researchers scoured the men’s genomes and identified 88 sites on the DNA that strongly correlated methylation to age. They replicated their findings in a general population of 31 men and 29 women between the ages of 18 and 70. Next, the scientists built a predictive model using two of the three genes with the strongest age-related linkage to methylation. When they plugged in the data from the twins’ and the other group’s saliva samples, they were able to correctly predict a person’s age within five years – an unprecedented level of accuracy.

While Dr. Vilain and his team envision the test becoming a forensic tool in crimescene investigations, it also could be used by physicians to evaluate the risk of age-related diseases in routine medical screenings and tailor interventions based on the patient’s bioage rather than his or her chronological age.

“Doctors could predict your medical risk for a particular disease and customize treatment based on your DNA’s true biological age, as opposed to how old you are,” Dr. Vilain says. “By eliminating costly and unnecessary tests, we could target those patients who really need them.”


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