By Deborah Kotz Globe Staff

Can high levels of stress really make you age faster? That seems to be the case judging by all the gray hair President Obama has sprouted over the course of his presidency. Researchers, though, have more scientific ways to measure aging, via telomeres -- the caps at the end of our cells’ chromosomes that protect DNA from damage. These caps shorten over time, and a new study suggests that a common form of anxiety is associated with shorter telomeres and perhaps an earlier risk of dying.

Brigham and Women’s Hospital researchers looked at data from 5,200 women participating in the Nurses’ Health Study and found that women with high levels of phobic anxiety -- an exaggerated fear of crowds, heights, enclosed spaces, and certain social situations -- had shorter telomeres on average compared with those of the same age who didn’t have this anxiety disorder.

The difference in telomere length was equivalent to women of the same chronological age being six years apart on the cellular level, according to Dr. Olivia Okereke, a psychiatrist at Brigham and Women’s Hospital who led the study. Previous research has tied telomere length to aging: Long telomeres have been associated with a lower risk of developing cancer and heart disease, as well as of dying at an earlier age.

“Those who have phobic anxiety tend to develop symptoms during childhood and their symptoms are usually chronic and long-lasting,” Okereke said. Previous studies suggest that short periods of stress don’t usually have much impact on telomere length, but anything that’s long-term or chronic could.

The latest research wasn’t able to identify whether the study participants with phobias were getting adequate treatment for their condition, and no studies have been conducted to see whether long-term measures to alleviate anxiety or other forms of chronic stress can affect telomere length. Researchers speculate that it would take at least a year to bring about some measurable change in telomeres.

Instead, a handful of studies have looked at whether short interventions to reduce stress can increase the production of an enzyme called telomerase, which repairs telomeres and maintains their length.

“Telomerase levels can change from moment to moment in response to a stressful situation or efforts to relax,” explained Jennifer Daubenmier, a psychologist at the University of California, San Francisco’s Osher Center for Integrative Medicine. She led a study last year to determine whether overweight women who said they had a tendency to overeat when stressed could raise their telomerase activity by learning how to practice mindfulness, a form of meditation that helps people focus on the present moment, whether they’re eating a strawberry or watching the clouds drift by overhead.

The pilot trial, which included 47 women who were randomly assigned to learn mindfulness or to be in a control group, didn’t show significant differences between the two groups in terms of a rise in telomerase -- possibly because the study was so small. Daubenmier said the size of the study made it impossible to determine whether the small increase seen in the treatment group was real or due to chance. But the researchers did find that telomerase levels rose more in those within the treatment group who took more of the mindfulness classes and that levels decreased in those who attended fewer than half of the 10 classes offered.

A 2008 study involving 30 men with early-stage prostate cancer, which Daubenmier also helped conduct, found that more intensive lifestyle changes did lead to a significant increase in telomerase levels after three months: the men took up regular exercise, engaged in relaxation breathing, and switched to a diet low in refined sugar and rich in whole foods, fruits, and vegetables, with only 10 percent of calories derived from fat.

Another study published last year found that daily meditation -- on the order of six hours a day for three months at a retreat -- led to a large increase in telomerase levels as well as improvements in mood and an increased sense of purpose in life. And other researchers recently found that just 12 minutes a day of formal meditation for eight weeks lowered stress levels and depression symptoms in full-time caregivers, as well as causing a significant rise in their levels of telomerase.

Studies have also shown that those who engage in regular exercise or other stress-reducing activities over the course of their lifetime tend to have longer telomeres than those who don’t.

What’s still unclear, said Daubenmier, is whether short telomeres actually cause our cells to die more quickly or whether they’re just a signal that our bodies are further along than we’d like in terms of our aging process. Until that’s determined, don’t expect drugs to preserve telomeres any time soon: better to meditate and exercise instead.

Deborah Kotz can be reached at dkotz@globe.com. Follow her on Twitter @debkotz2.