Based on studies like these, some researchers think that telomere length could predict life span better than traditional measures.
"Cholesterol tests just tell you about your lipid profile, glucose tests just tell you about blood sugar, and C-reactive protein just tells you about inflammation," Epel said. "Telomere length is a more summative measure for multiple biochemical imbalances, a global marker of health status."
Dr. Robert Sapolsky, a neurology professor at the Stanford School of Medicine who was not involved in these studies, agrees. "Telomere measures are a good time-integrated marker of bad news, as opposed to those other factors being somewhat more acute." They indicate "systemic wear and tear."
But how broadly useful such a marker, which is still just a research tool, would be is unclear -- because no one knows whether telomere length in immune cells reflects those in other tissues. So while blood cells can provide relevant information about cardiovascular disease and diabetes risks, they may not indicate much about the aging brain or Alzheimer's disease.
There is good news and perhaps a lesson amid the findings about telomere length. Some people in the study actually had their telomeres lengthen instead of shorten. This study did not measure telomerase levels, but a small pilot study by Blackburn, Epel and others of 30 men published last November in the Lancet suggests it is possible to elevate telomerase levels naturally and reverse the ill effects of unhealthy living on telomeres. Comprehensive lifestyle improvements -- including a low-fat diet, regular exercise and stress reduction through meditation and yoga -- increased telomerase activity levels by 30% after three months.
"Unhealthy living could increase factors that damage the telomeres' DNA," said Dr. Emanuel Skordalakes, assistant professor at the Wistar Institute, an independent biomedical research institute in Philadelphia. "By living healthier they were able to increase levels of telomerase activity, which can take care of that damage and which in turn should increase the length of telomeres."
Three months was too short a time to expect to see such increases, but whether that could be a longer-term outcome that could reduce the risk of dying from a chronic disease is one of the questions that researchers are trying to answer.