Science and Technology

Geneticists predict age with accuracy using only a saliva sample

With saliva samples the researchers analyzed the methylation patterns and were able to determine the age of persons

The discovery offers a multitude of possible applications. A newly patented test based on the research, for example, can offer researchers a new crime scene forensic tool to identify the age of a suspect.

"Our approach provides an answer to the ongoing search for reliable markers of aging. With only a saliva sample, we can accurately predict the age of a person without knowing anything about it," said Dr. Eric Vilain, professor of human genetics , pediatrics and urology.

Vilain and his colleagues examined a process called methylation, a chemical modification of one of the four blocks that make up our DNA.

"Genes partially define the way our bodies age, but also environmental influences can change our DNA as we age. Methylation patterns change as we age and contribute to age-related diseases," said Vilain.

Using saliva samples collected from 34 pairs of identical male twins aged between 21 and 55, researchers at the University of California investigated the genomes of men and 88 stretches identified in the DNA that correlated strongly with age methylation. They said their findings in a general population of 31 men and 29 women between the ages of 18 and 70 years.

Next, the scientists constructed a predictive model using two of the three genes that had the link between age and methylation stronger. When the data from the connected twins and saliva samples from the other group, they were able to correctly predict the age of a person with an unprecedented level of accuracy (within a margin of five years).

"The relationship of methylation with age is so strong that we can identify someone's age by examining only two blocks from 3 billion to make up our genome," said geneticist Sven Bocklandt.

Vilain and his team envisage the test becoming a forensic tool in crime scene investigations. Through analysis of traces of saliva left on a bite or a cup of coffee, laboratory specialists could predict the age of a criminal suspect.

In a minority of the population, the methylation does not correlate with chronological age. Using the data they are gathering in this population, scientists may one day be able to calculate the "biological age" of a person, the measure of a person's biological age versus chronological age.

Doctors can assess the risk of age-related diseases in routine medical examinations and shape interventions based on bio-patient age rather than chronological age. Instead of requiring everyone to undergo a colonoscopy at age 50, for example, doctors recommend preventive examinations according to the bio-age of each person.

"The doctors could predict the risk for a particular medical disease and customize treatment based on the true age of your biological DNA, rather than rely on their chronological age to do so. By eliminating unnecessary and expensive tests, we target those patients who really need them, "said Vilain.

The team is currently exploring whether people with a lower bio-aged live longer and suffer less illness. They are also examining whether the reverse is true - if a bio-aged is linked to an increased rate of disease and early death.