NEW YORK (AP) _ The tips of the chromosomes in many cells shrink as you age, and a preliminary study now suggests the shrinkage might promote death from age-related disease.
Scientists found that people older than 60 who showed shorter-than-average chromosome tips were nearly twice as likely than others to die over the next 15 years or so, especially from heart disease and pneumonia.
Experts called the finding intriguing but cautioned that the study was far too small to let anybody draw conclusions.
Chromosomes are the inherited lengths of DNA that contain genes. At their tips are DNA stretches called telomeres (pronounced TEE-loh-meers). Each time a cell divides, each chromosome makes a copy of itself, and the telomeres shrink slightly. Once they get short enough, cells lose their ability to divide.
In 1998, researchers made headlines by showing they could block that process and keep cells young and dividing indefinitely by giving them an enzyme called telomerase. While that led to public speculation about making people live dramatically longer, scientists are focusing on prospects for treating specific diseases by rejuvenating certain tissues.
The new work impressively bolsters the case that telomeres might play a role in human aging, said one expert, Dr. Woodring Wright of the University of Texas Southwestern Medical Center at Dallas. But like other scientists, he said the study must be repeated with many more participants to get a firmer result.
The study is reported this week in the journal Lancet by Dr. Richard Cawthon and colleagues at the University of Utah. They noted that telomere shortening, rather than promoting disease, might just be a symptom of other processes that actually affect the risk of disease.
The study focused on 143 Utah residents who were 60 or older when they gave blood between 1982 and 1986. Researchers studied their stored blood to measure how long telomeres were in blood cells at that time, and they consulted death records to see which donors went on to die by the middle of 2002.
In all, 101 donors died. People with shorter telomeres showed an 86 percent higher death rate. They ran a threefold higher risk of dying from heart disease and an eight-fold higher risk of death from infectious disease, almost entirely pneumonia.
Their rates of death from stroke and cancer were higher, but by too little to be considered meaningful.
Only eight donors died from infectious disease, but Cawthon noted the association with telomere length was particularly strong. That might mean that short telomeres had left immune system cells with less capacity to multiply for fighting off infections, he said.
A person with short telomeres in blood cells may also have short ones in other tissues, which could raise the risk for other diseases, he said.