From before we take our first breaths, we are aging. We often mark this passage of time by counting gray hairs, smile lines and birthday candles. Biological clocks, however, attempt to measure how our bodies respond to the passing years, which could be much faster or slower than our chronological age. 

“Biological age is basically resilience,” explained Tamar Tchkonia, PhD, co-director of the Cedars-Sinai Center for Advanced Gerotherapeutics and director of the Facility for Geroscience Analysis. “As we age, we become more vulnerable to environmental and bodily stress.”

At a cellular and molecular level, our hardworking cells wear down over time. Biological aging triggers inflammation and tissue scarring that disrupt how our bodies heal and regenerate. Proteins and age-damaged cells can build up, while our DNA undergoes changes that lead to genetic instability. These progressive “hallmarks of aging” are tied to dozens of diseases, including arthritis, Alzheimer’s disease, cancer, diabetes and osteoporosis.

As medicine gets closer to understanding what happens as we age, biological clocks attempt to shed light on your body’s true age and health risks.

Chemical tags on our DNA control how our genes read their instructions and act. Like a light switch, they turn some genes on (methylation) and others off. Over time, the genes that our DNA read shift, and more and more go dark. 

Epigenetic clocks, the most popular type of biological clock, measure these patterns to estimate how a person’s body is aging. Studies suggest a link between this estimate and risk of serious conditions such as cancer, heart disease, frailty, disability and cognitive decline. 

Other biological clocks and calculators test blood-based proteins, lipids and metabolites, potentially predicting both long-term health and lifespan.

Director of the Cedars-Sinai Center for Geroscience Sara Espinoza, MD, is currently using epigenetics to evaluate whether metformin, a drug used to treat diabetes, shows promise in slowing aging.

Despite this potential, experts urge caution. 

“There isn’t a lot of evidence yet that an epigenetic or biological age clock is something we should be following clinically,” Espinoza said. “We don’t really know how helpful they are to the average person. Right now, there isn’t evidence to support using these tools to make healthcare decisions.”

If you decide to buy a biological age test online, take your results with a pinch of salt. 

“Different organs age at different rates,” Tchkonia said, and in many different ways.

Cedars-Sinai researchers are zeroing in on a large pool of signals for aging, including gene, protein and metabolism changes as well as inflammation. They are studying these measures across more than 40 worldwide clinical trials to confirm their link to aging, with plans to translate them into more specific and accurate tests. Scientists hope these screenings could one day predict your likelihood of developing certain age-related diseases and detect them, as well as your risk for fast aging.

In her lab, Tchkonia is exploring the association of aging markers in our blood, brain and spinal cord fluid, urine and saliva, with medical tests of liver, kidney and heart function and memory.

“We are trying to marry these together, then create composite aging scores,” she said.

This multilayered approach can help scientists determine the body’s age. An endlessly unfolding array of exposures—even experiencing preeclampsia in pregnancy and taking certain medications—can alter your cells and speed up the aging process. You could seem five years younger than the age listed on your driver’s license—a win—but your blood pressure or cholesterol levels might tell a different story.

Researchers hope to identify aging patterns that could guide groundbreaking treatments which directly target aging, beyond just adding years.

“Our goal is to help people live not just longer but also healthier, so they can enjoy life,” Tchkonia said.

For a clearer picture of your “true” age, experts focus on your ability to use your body and mind. This “physiological age” approach looks at how well both support your activities of daily living.

Balance and strength are good indicators of future health—such as frailty and broken bones or even death after a fall—and often get better when you do specific exercises. Tests include:

• Gait speed, over a 10-foot walk. “If we only did one thing, we would measure gait speed,” Espinoza said. 
• Chair rises from a sitting position, determining muscle and grip strength.
• Six-minute walk, to capture endurance.
• Five-minute cognitive test of attention, memory, speech and brain health.

Espinoza, who is launching a new Cedars-Sinai healthspan clinic, encourages you to think about both your biological and physiological age as a jumping-off point to examine your lifestyle. Then, work with your doctor to implement proven healthy aging habits, such as not smoking, eating a nutritious and anti-inflammatory diet, and getting regular exercise.