No one can change their chronological age, or how much time has passed since they were born, but a person’s biological age—measured by the state of their DNA—can be increased by several factors, including stress. A higher biological age can raise the risk of certain diseases or death.
But a new study of mice and humans offers some hope on this front: After a stressor subsides, researchers suggest, biological age can fall once again.
“That’s the thing that a lot of people didn’t think was possible; they thought once you start climbing that ladder, there’s no way to get back,” James White, a cell biologist at Duke University and a co-author of the study, tells the Scientist’s Alejandra Manjarrez.
In a sense, though, the new finding is not unexpected, as Tunc Tiryaki, a plastic surgeon and founder of the London Regenerative Institute, tells Healthline’s Victoria Stokes. “Our bodies have the ability to repair and recover from damage caused by stress, so it makes sense that this recovery process can also restore our biological age,” he tells the publication.
Stress can cause physical impacts to the body, such as increased heart rate and blood pressure, the release of adrenaline and production of the hormone cortisol. If adrenaline and cortisol levels are elevated for an extended period of time, that can damage DNA and cells.
In the new paper, published in April in the journal Cell Metabolism, researchers measured biological age by looking for changes in DNA’s structure connected to aging, per Live Science’s Sascha Pare. Known as DNA methylation, this process adds molecules to DNA that can affect a person’s health risks.
In the first stage of the research, the scientists surgically attached three-month-old mice to 20-month-old mice so that blood could flow between each pair of rodents. Over three months, the biological age of the younger mice increased while they shared blood with their older counterparts. But after the young mice were detached and allowed to recover for two months, the change in their biological ages reversed.
Then, the researchers looked at human DNA from blood samples gathered in previous studies to measure how human bodies react to stress.
In one stage, the researchers examined blood samples from elderly patients who had undergone major surgeries. Patients who received emergency surgery for a fractured hip had an increased biological age the morning after the procedure, but it returned to pre-surgery levels four to seven days later. However, the researchers did not find the same effect in patients who had undergone elective hip surgery or colorectal surgery.
The team also found that biological age increased during pregnancy. But after giving birth, people saw their biological age return to pre-pregnancy levels in about six weeks on average, per Live Science.
Finally, the researchers looked at patients who had been hospitalized with Covid-19, but these results varied by sex. While the biological age of female patients dropped within two weeks of recovery, that of men did not.
The study was unique in that it looked at biological age both before and after stressful events, researchers say. “There are just very, very few studies that have looked at these clocks before and after some kind of intervention,” Daniel Belsky, an epidemiologist at Columbia University who did not participate in the study, tells the Scientist. The collection of “data before and after measurements of a large variety of interventions is a really powerful step.” Belsky peer reviewed the study and is collaborating with some of the authors on unrelated research, according to the publication.
The study shows that biological age is “much more dynamic than people previously thought,” Jesse Poganik, a co-author of the study and a chemical biologist at Harvard University, tells Live Science. “You can have these very severe stress events, which trigger an increase in the biological age, but it can be short-lived, if the stress is short-lived, and then the age can be restored.”