A new finding may explain how stress could ultimately lead to premature aging.

Chronic psychological stress is associated with accelerated shortening of the caps, called telomeres, on the ends of chromosomes in white blood cells - and thus hasten their demise - according to a report in the Proceedings of the National Academy of Sciences.

Telomeres promote chromosome stability, Dr. Elissa S. Epel at the University of California, San Francisco, and her colleagues explain. Telomeres shorten with each replication of the cell, and cells cease dividing when telomeres shorten sufficiently.

The team investigated the theory that psychological stress affects telomere shortening and thereby contributes to accelerated aging.

Their study included 39 healthy, premenopausal women who were primary caregivers for a child with a chronic illness, and 19 age-matched mothers of healthy children who served as a comparison “control” group.

Stress was measured with a standardized questionnaire, and telomere length was measured in participants’ blood samples.

Within the caregiving group, the longer that a woman had been a caregiver, the shorter was the length of telomeres.

In the 14 women with the highest stress scores, telomeres averaged 3,110 units in length; the 14 with the lowest stress had telomeres that averaged 3,660 units.

In adults, telomeres shorten by an average of 31 to 63 units per year, so the scientists estimate that the 550-unit shortening in the high-stress group translates to 9 to 17 additional years of aging.

These findings may have implications for human health, co-author Dr. Elizabeth H. Blackburn, also at UCSF, told Reuters Health, since telomere shortening is associated with premature death from cardiovascular disease and infections.

While the number of years that mothers had been a caregiver did matter, “not all caregivers fell into the high-stress group,” she added. “This points to the importance of trying to use stress reduction interventions as much as possible.”

SOURCE: Proceedings of the National Academy of Sciences, online November 29, 2004.