The protective caps on the ends of chromosomes called telomeres may portend a higher risk of death. A new, large study,The Genetic Epidemiology Research on Adult Health and Aging (GERA), reports data on telomere lengths and genotypes of over 675,000 SNPs for each of 100,000 subjects.
Telomeres prevent a chromosome’s DNA from being eaten away or damaged. Previous studies have shown that telomeres shorten with age and have linked short telomeres with several diseases. However no one has previously reported whether truncated telomeres cause health problems or are a side effect of aging and poor health.
To better understand, researchers at Kaiser Permanente and the University of California, San Francisco measured telomere length in 110,266 people in northern California. The participants were part of an ongoing project that explores links between genetics and health. This study is the largest ever to examine the role of telomeres in health.
The 10 percent of people with the shortest telomeres had a more than 20 percent higher risk of dying than people with longer telomeres, reported November 8 at the annual meeting of the American Society of Human Genetics. The study suggests that once your telomeres become critically short, your risk of dying increases. The increased death risk is about the same as for people who drink 20 to 30 alcoholic beverages per week or smoke for 20 to 30 years. The increased risk is small, but significant.
Telomeres do shorten with age, the study confirms, but men older than 75 and women over age 80 tended to have longer telomeres than their slightly younger counterparts. The result seems counterintuitive, and does not mean that telomeres start to grow in length once people reach a certain age. Rather, the finding probably means that people with shorter telomeres died before they reached those ripe old ages and the survivors are those that carry longer telomeres.
African-Americans tended to have longer telomeres than European-Americans, Latinos or Asians, the researchers found. The reason for that difference is not clear. As expected, people who smoked or drank heavily were more likely to have shorter telomeres, and higher levels of education were associated with longer telomeres. Other studies have linked exercise with longer telomeres, but Dr. Schaefer, the PI, and her colleagues found no such association.
One of the study’s findings is rather puzzling: Higher body mass index, or BMI, was associated with longer telomeres. Although a high BMI is not healthy, more work will be needed to understand the relationship between body size and telomere length.
While the study is important, over reaching conclusions should not be drawn given the study used the biomarker of telomeres taken from saliva samples. Telomeres from cells in other parts of the body, something hard to sample in human studies such as this one, will be one, amongst other additional studies that are required to better understand telomeres in aging and health.