Nov. 29, 2004 -- Chronic stress takes a toll on the body, triggering premature aging of immune system cells, new research suggests.
"People who are stressed over long periods tend to look haggard, and it is commonly thought that psychological stress leads to premature aging and other ... diseases of aging," writes lead researcher Elissa S. Epel, PhD, a professor of psychiatry at the University of California at San Francisco (UCSF).
But exactly how chronic stress "gets under the skin" to do its damage has not been understood, Epel writes. Chronic stress, the focus of numerous studies, has been linked with poor health, heart disease, and lower immunity.
Epel's study appears in the latest issue of Proceedings of the National Academy of Sciences.
In it, Epel and her colleagues examine one sign of biological aging -- tiny segments of DNA and protein, called telomeres, that cap the ends of chromosomes. Each time a cell divides, a portion of this DNA erodes. After many cell divisions, so much DNA is missing - and the telomeres are so short -- that the aged cell stops dividing, she explains.
As cells age, they produce less and less telomerase, an enzyme that adds DNA onto the telomeres. Both telomere length and telomerase levels can therefore indicate a cell's "age," she writes. That's when risk of disease increases.
"The results were striking," says co-author Elizabeth Blackburn, PhD, professor of biology and physiology at UCSF, in a news release. "This is the first evidence that chronic stress - and how a person perceives stress - may damp down telomerase and have a significant impact on the length of telomeres ... [causing] cellular aging."
Chronic Stress and Mothers
To look more closely at whether chronic stress leads to telomere shortening, Epel and her colleagues focused on 58 healthy women, all either mothers of a healthy child or "caregiving mothers" of a chronically ill child.
The mothers completed a brief questionnaire about chronic stress in their lives over the past month. Then a blood sample from each was analyzed to determine telomere length and telomerase activity.
As expected, surveys showed that caregiving mothers had higher stress levels than mothers of healthy children.
Total years spent tending a sick child made a big difference. More caregiving years translated into shorter telomeres and lower telomerase activity.
But there was another key finding in the study: A mother's telomere length was related to her perceived stress level -- whether her child was chronically ill or not.
In translating telomere length into years of aging, researchers determined the cells from the highly stressed mothers had aged from nine to 17 additional years compared with the cells from the low-stress mothers.
"The exact mechanisms that connect the mind to the cell are unknown," writes Epel. "While psychological stress seems to cause telomere shortening and cell aging, it's possible that some people are less vulnerable to [chronic] stress - and therefore have longer telomeres."