Telomeres are protective strings of DNA that cap the ends of chromosomes. Over time, cell division and oxidative attacks cause telomeres to shorten. There is a connection between short telomeres and cellular aging; when telomeres reach a critical shortness, cell function is impaired and eventually, cells die. Scientists have found links between short telomeres and smoking, obesity, diabetes, high blood pressure, cancer, heart disease and susceptibility to infectious diseases.
Andrew Steptoe of University College London and his colleagues have found that telomere length can predict how long it takes older men to recover from stressful situations. Men with shorter telomeres have longer recovery times than men with longer telomeres. This could mean that men with shorter telomeres suffer from chronic stress.
Studies also show a correlation between psychological stress and short telomere length. Steptoe and his team wanted to understand why this correlation exists. They were particularly interested in an enzyme called telomerase (TA). This enzyme makes telomeres longer. It becomes more active in times of acute mental stress. Short telomeres and high TA activity could be a sign of a stressed system.
The researchers divided 333 healthy men and women between the ages of 54 and 76 into three groups, those with longer telomeres, those with shorter telomeres and low TA activity and those with shorter telomeres and high TA activity. All the subjects were given tasks designed to cause psychological stress.
When they performed the tasks, all the subjects experienced an increase in heart rate and blood pressure. Their levels of cortisol, a stress hormone, also rose. However, once the task was completed, some men found it easier to recover and return to normal conditions than other men. Men with longer telomeres had quicker recovery times than men with shorter telomeres. Men with shorter telomeres and low TA activity had quicker recovery times than men with shorter telomeres and high TA activity.
Psychological testing showed that men in the short telomere/high TA group were more hostile and less optimistic than other men. They also had less social support. The researchers think these men found it harder to recover from stress because they were carrying a high allostatic load. That is, chronic stress had caused the their regulatory processes to become disturbed.