Age may be just a number in dating, but you can’t fool biology. Researchers at the Boston University School of Medicine (BUSM) have devised a specialized eye scanner that can detect certain proteins in the retina that track biological aging in living humans, with important implications for clinical medicine.

Although two people might have been born at the exact moment in time, they will age differently depending on their genetics, upbringing, and other environmental factors.

The fact that people age at different rates is rather common knowledge, but measuring an individual’s biological rate of aging has proven extremely challenging. So far, there hasn’t been any single marker or noninvasive method that has been certified to accurately measure and track biological aging in humans — but that may be set to change.

In a new study, which appeared in the Journal of Gerontology: Biological Sciences, researchers at Boston University describe an eye scanner that analyzes proteins found in the lens that accumulate age-related changes throughout life.

“These lens proteins provide a permanent record of each person’s life history of aging. Our eye scanner can decode this record of how a person is aging at the molecular level,” Lee E. Goldstein, associate professor of neurology, pathology & laboratory medicine, psychiatry and ophthalmology at BUSM, and lead author of the new study said in a statement.

“We showed that this eye scanner detects molecular aging in living humans across a wide age range. We also used experimental test tube studies to confirm that the signals from the scanner detect molecular aging of human lens proteins,” Goldstein wrote in an e-mail to ZME Science.

Why do people age differently?

When we come into this world, each of us is offered an imaginary clock whose tick-tocks beat to the tune of life. Each clock is unique to every person because the pace at which the clock dials turn is different — and biostatisticians at the University of California, Los Angeles (UCLA), think that epigenetic changes in the genome play a major role.

In a 2016 study, researchers at UCLA led by Steve Horvath analyzed blood samples from more than 13,000 Americans and sequenced their genomes. Within this sample size, 2,700 participants had died.

While smoking, blood pressure, and body weight were all reliable predictors for life expectancy, the researchers also identified the ‘aging rate’ as another important factor.

In other words, some die younger or older simply because their biological clock is ticking faster or slower.

“Our findings show that the epigenetic clock was able to predict the lifespans of Caucasians, Hispanics and African-Americans in these cohorts, even after adjusting for traditional risk factors like age, gender, smoking, body-mass index and disease history,” said Brian Chen, the study’s first author and a postdoctoral fellow at the National Institute on Aging.

The researchers found that for 5 percent of the population that ages the fastest, there’s a 50 percent greater average risk of dying at any age. For instance, Horvath mentions a fictitious case study involving two 60-year-old men. Pete is ranked in the top 5 percent of the population that ages the fastest while Joe is classed in the 5 percent of the population that ages the slowest. If both lead stressful lives and smoke tobacco, then Pete has a 75% chance of dying in the next 10 years compared to just 46% chance for Joe.

Horvath, who is 48 years old, took his own test and found he’s actually five years older, biologically speaking.

In contrast to genetic methods, the new eye scanner demonstrated by the Boston University assesses biological aging in a non-invasive manner, using a more straightforward method that has a “very good, better than anticipated” accuracy, according to Goldstein. In the future, a doctor might scan a patient’s retina to determine their biological age to offer more personalized medical care.

“By contrast, eye scanning technology that probes lens protein affords a rapid, noninvasive, objective technique for direct measurement of molecular aging that can be easily, quickly, and safely implemented at the point of care. Such a metric affords potential for precision medical care across the lifespan,” Goldstein said.

The eye scanner took almost two decades to develop, with work on it first starting in 2003. Srikant Sarangi, co-author of the new study and a Ph.D. student at Goldstein’s lab, had to take daily measurements for nearly a year. He only took a break while visiting family, and this actually shows in the experimental data.

“You can also see Srikant’s exceptional accuracy during the period preceding his trip home and relative brief rustiness on his return. Not often that you get this signature of the experimental process reflected in such an exceptional experiment. Like minor imperfections in a Rembrandt painting,” Goldstein wrote.

Next, the research team plans on conducting large clinical trials to validate their method and device.