Scientists may have found a piece of the puzzle that explains why some lucky people almost never get sick, according to a new study published Wednesday in the Journal of the American Medical Association.
Researchers isolated a biological marker that appears to predict who is most susceptible to catching colds, and they hope the finding will lead to the discovery of lifestyle changes that people can make to better protect their immune systems and prevent them from getting sick.
“The provocative finding is that this is a very stable marker of disease susceptibility that begins to emerge in early adulthood,” says the study’s lead author, Sheldon Cohen, a professor of psychology at Carnegie Mellon University in Pittsburgh.
The study followed 152 healthy volunteers between the ages of 18 to 55 who were given nose drops containing rhinovirus to intentionally expose them to the common cold virus. The volunteers were then quarantined for five days, with each being paid $1000 for their participation in the study.
Prior to being exposed to the virus, the volunteers were asked to give a blood sample to allow Cohen and his colleagues to take a closer look at a certain type of white blood cell known for its ability to fight off viruses. Like all cells, these immune cells have structures called telomeres, which are protective cap-like protein complexes at the ends of chromosomes.
The study found that the length of the telomeres predicts resistance to upper respiratory infections in young and middle-age adults. Telomere length is a biomarker of aging. As the cell's telomeres shorten, it loses its ability to function normally and eventually dies. Therefore, the scientists explained, white blood cells with short telomeres don’t work as well and have trouble making copies of themselves to fight off infections.
After tracking the length of the volunteer patients exposed to the cold virus, the scientists found that 69 percent of them had developed respiratory infections 5 days later – and 22 percent had developed actual symptoms of a cold, including congestion and increased nasal discharge.
In the volunteers with the shortest telomeres, the rate of infection was 77 percent compared with 50 percent among those with the longest telomeres.
"Our work suggests the possibility that telomere length is a relatively consistent marker across the life span and that it can start predicting disease susceptibility in young adulthood," said Cohen. "We knew that people in their late 50s and older with shorter telomeres are at a greater risk for illness and mortality. We also knew that factors other than aging, such as chronic stress and poor health behaviors, are associated with shorter telomeres in older people. Consequently, we expected that younger people would vary in their telomere length as well and wanted to see what this would mean for their health."
Moreover, researchers found that telomere length became even more important in determining whether volunteers in the study would get sick as they aged. Beginning at approximately age 22, telomere length started to predict whether they'd develop infections.