On the tip of each chromosome in each cell in our bodies is a stretch of DNA, a little tail called a telomere that shortens as we age. How quickly it shortens predicts the cell’s — and our — longevity.

Elissa S. Epel, Ph.D,  a 2002 NARSAD Young Investigator, studies the effect of stress on cell aging. Last year, she and colleague Dr. Elizabeth Blackburn made news: they found that people, most often women who care for ill relatives, or in similarly stressful situations, age more rapidly than normal. They detected this difference at the genetic level: caregivers under stress tended to have shorter telomeres.

When the body’s immune system overproduces the hormone cortisol, Dr. Epel noted, mood and health tend to be affected, no matter a person’s age. Childhood trauma, for example, can have consequences that last a lifetime. Over the past decade, Dr. Epel and colleagues have measured telomeres in different groups of people. For instance, they have looked at mothers caring for children with autism or other illnesses. Among these women, those who felt overwhelmed had telomeres of a length that might have been expected if they had aged 10 additional years. This dramatic finding was confirmed in subsequent human and animal studies.

Can the effects of stress on telomeres be mitigated? Dr. Epel discussed factors that appear to promote resilience to stress. Attitude can be an important factor: Do you experience a situation as threat or challenge? Do you feel in control and that your efforts are worthwhile? Another powerful factor, Dr. Epel said, is exercise. Among a group of older women under stress, including some who were caring for family members with dementia, she found that those who exercised vigorously had significantly longer telomeres than those who were inactive.

In “Know Your Telomeres,” a novel program she is starting, Dr. Epel is recruiting women aged 50 to 65 who will be tested and then told their telomere length. The question of interest is how this information will affect the women psychologically for better or worse. Will it lead to complacency or distress? Will it promote changes in lifestyles and habits? The women will then be retested a year later.