Testing the length of the ends of your DNA strands may not be the best predictor of how long you will live, a new study suggests.
Instead, simpler measures that include your age and your ability to climb stairs or walk a short distance may more accurately pinpoint longevity, researchers report.
The study team analyzed death rates over five years among older people in the United States (60 and older), Costa Rica (61 and older) and Taiwan (53 and older).
The aim was to find out how a broad set of basic measures -- such as age, mobility and smoking habits -- compared with gauging the length of telomeres in predicting death over a five-year period. Telomeres are the ends of DNA that shrink with age, the researchers said.
Since the discovery that telomeres act as a "molecular clock" in people, there has been great interest in finding out if telomere length can be used to accurately predict when someone will die, the scientists explained.
But this new study found that using telomere length was just slightly better than a "coin toss," the researchers said. Actual age was, by far, the single best predictor of death, according to the findings published online April 6 in the journal PLoS One.
"Scientific evidence on telomere length has been sensationalized and, in some cases, exaggerated by the media and by companies that have capitalized on the research to market products that may promise more than they can deliver," said study author Dana Glei. She is a senior research investigator at Georgetown University's Center for Population and Health, in Washington, D.C.
Study co-author Noreen Goldman is a professor of demography and public affairs at Princeton University. She said in a Princeton news release, "We were surprised that most indicators outperformed telomere length, including self-reported measures of health and mobility, an assessment of cognitive [mental] function, smoking, exercise, an inflammatory marker and a measure of kidney function."
The findings show there is no evidence to suggest that doctors should test telomere length to determine how long patients will live, the study authors said.
"It is much easier and less expensive to ask someone's age than to collect blood, extract DNA and measure telomere length," Glei said in the news release.
The study results are also important for consumers, the researchers said.
"On the Internet, they sell test-your-own-telomere-length kits and supplements that are touted to help people maintain their telomeres. We caution buyers to beware," Glei added.