Shorter Telomeres Predict Increased Mortality
Telomeres are the ends of chromosomes, the strands of DNA that contain our genes. As cells reproduce, the telomeres normally shorten; the only exception is our egg and sperm cells. This shortening contributes to ultimate self-destruction of these cells.
Although telomere shortening only affects cells that normally reproduce (chromosomes in mature nerve cells, for example, have stable telomeres), some scientist feel that the process plays a key role in aging. This theory is supported by a genetic disorder known as dyskeratosis congenita. Patients with this disorder are born with short telomeres and experience accelerated aging, the premature onset of age-related disease, and early death. Until now, no one has studied whether people in the general population with longer telomeres live longer than those with shorter telomeres.
In a study published in the February 1, 2003 The Lancet , scientists from the University of Utah and the Huntsman Cancer Institute have found that people with shorter telomeres are at an increased risk of overall death, death from ]]>heart disease]]> , and death due to infectious diseases, compared to people with longer telomeres.
About the Study
The scientists studied 143 men and women, aged 60-97 years, who had donated blood between 1982 and 1986, and for whom follow-up survival data was available. The study participants were not selected for the presence or absence of any disease or disorder.
The researchers analyzed telomere lengths from blood DNA; blood telomere length has been shown to correspond with telomere lengths in other body tissues. Telomere lengths were grouped into halves and quartiles, from shorter to longer, and were further subdivided by categories of age (60– 64 years, 65—69 years…85 years and older).
When matched by age, individuals in the bottom half of telomere length were twice as likely to die as those in the top half of telomere length. Women with longer telomeres lived an average of 4.8 years longer than women with shorter telomeres, and men with longer telomeres lived and average of 4.0 years longer than men with shorter telomeres.
Study participants in the bottom half of telomere length were three times as likely to die of heart disease as those in the top half. And individuals in the bottom 25% of telomere length were eight times as likely to die of infectious disease as those in the top 75% of telomere length.
How Does This Affect You?
This study draws a compelling connection between telomere length and lifespan. However, it remains to be seen whether telomere shortening contributes to mortality, or whether it is a marker of one or more age-related diseases or conditions already present.
It is much too early to recommend that you have your telomere lengths measured. One day, however, telomere length assessments may become a useful way to predict future health risks. And, if it turns out that telomere length is a contributing factor to longevity, the ultimate goal would be to figure out a way to lengthen short telomeres. Until then, suffice it to say that when it comes to telomeres, size does matter.
National Institute on Aging
National Institutes of Health
Cawthon RM, Smith KR, et al. Association between telomere length in blood and mortality in people aged 60 years or older. The Lancet . 2003;361:393-395.
Last reviewed Jan 30, 2003 by ]]>Richard Glickman-Simon, MD]]>
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