Stress linked to aging cells

Stress can speed up the aging process, according to a new US study. Scientists based at the University of California have found that cells taken from women who experience high levels of stress appear years older than their actual biological age. The research, published in the Proceedings of the National Academy of Sciences, shows that the genetic material in the body cells of stressed women shows more signs of 'wear and tear' than that of women who report lower stress levels.

The researchers studied 58 healthy women aged between 20-50 years, 19 of whom had a healthy child and 39 of whom had a child with a long-term, serious illness. They looked at the ends of the chromosomes (bundles of genetic material found in almost every body cell) present in white blood cell samples taken from the women. In particular, they measured the length of the protective 'caps', called telomere, found at the ends of the chromosomes. They found that in all the women, the telomeres were shorter in those who reported higher levels of stress. And in the group with ill children, the team found that the longer a woman had spent caring for a child, the shorter her cells' telomeres were likely to be.

It has long been known that telomeres act as a kind of cellular clock, marking the number of times a cell has replicated its genetic material. Each time a cell divides to make two new cells, its telomeres get shorter, until eventually it stops multiplying altogether. So the length of a cell's telomeres, measured in chemical 'letters' of DNA, reflects the age of the parent cell. A study published last year suggested that people with shorter telomeres may die earlier than those with longer telomeres. Some cloned animals have shorter telomeres than expected for their age, indicating they may have a shortened lifespan.

In the latest study, the Californian team show that long-term psychological stress may cause harm by increasing the rate of cellular aging. In those women who reported the highest levels of stress, the telomere length suggested their body cells had aged by an average of an extra ten years, compared to their biological age. Also, the activity levels of a substance called telomerase, which replenishes the telomeres of newly divided cells, was lowest in the women undergoing most stress. 'Chronic stress appears to have the potential to shorten the life of cells, at least immune cells (white blood cells)', said study author Elissa Epel.

Although it's not yet clear how stress can affect telomeres, the scientists think that stress hormones may play a role. The team now plans to see if long-term stress affects the telomeres of other types of cell, such as those that make up the heart blood vessels. They also want to study the long term effects of stress on the immune system cells, to find out how it affects telomerase levels. Epel say if the findings are confirmed, then it could be possible to intervene, offering therapies such as yoga or meditation to try and counter the telomere-shortening effects of stress. The research also suggests that drugs that increase telomerase activity could be used to reduce the risk of disease in individuals with short telomeres.