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November 11, 2011

BehindTheMedspeak: Your saliva can predict your age



Scientists from my alma mater (UCLA Medical School — GO BRUINS!) have developed a test which can accurately predict a person's age from a saliva sample without knowing anything else about the person.

Excerpts from a Discover Magazine story about the work follow.

 The researchers began by taking saliva samples from 34 pairs of identical male twins between the ages of 21 and 55 years old.

[They] focused their attention on methylation, a chemical process where a methyl group (a carbon atom bonded to three hydrogen atoms) attaches to a gene and affects how it turns on or off. Unexpectedly, the team found that the degree of methylation in certain areas of the genome increased with the age of the twins. They repeated their experiments with a population of singletons and found the same pattern.

The scientists then identified the two genes that had the strongest age-related link to methylation, and used them to build a predictive model. When they plugged in data from the saliva samples, they were able to predict people’s ages to within five years.

In previous studies, scientists noticed significant DNA methylation differences in people with age-related diseases, [and the UCLA team] are now studying how biological age relates to health. They are looking at whether people with lower biological ages live longer and suffer fewer diseases than their peers with higher biological ages.

Below, the abstract of the scientific paper, published online in June 2011 in PLoS ONE.

Epigenetic Predictor of Age

From the moment of conception, we begin to age. A decay of cellular structures, gene regulation, and DNA sequence ages cells and organisms. DNA methylation patterns change with increasing age and contribute to age related disease. Here we identify 88 sites in or near 80 genes for which the degree of cytosine methylation is significantly correlated with age in saliva of 34 male identical twin pairs between 21 and 55 years of age. Furthermore, we validated sites in the promoters of three genes and replicated our results in a general population sample of 31 males and 29 females between 18 and 70 years of age. The methylation of three sites—in the promoters of the EDARADD, TOM1L1, and NPTX2 genes—is linear with age over a range of five decades. Using just two cytosines from these loci, we built a regression model that explained 73% of the variance in age, and is able to predict the age of an individual with an average accuracy of 5.2 years. In forensic science, such a model could estimate the age of a person, based on a biological sample alone. Furthermore, a measurement of relevant sites in the genome could be a tool in routine medical screening to predict the risk of age-related diseases and to tailor interventions based on the epigenetic bio-age instead of the chronological age.

For those who prefer their science unabridged, you can read the paper in its entirety, along with tables, figures, and references, here.

November 11, 2011 at 02:01 PM | Permalink


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