RENEE MONTAGNE, Host:
This is MORNING EDITION, from NPR News. I'm Renee Montagne. Good morning.
MONTAGNE: Still, as NPR's Allison Aubrey reports, researchers have pinpointed a few things you can do to cut your chances of getting sick.
ALLISON AUBREY: There's always somebody passing around a cold virus, whether it's a stranger who sneezes in the elevator, or a sick colleague who lends out a pen covered in germs. But here's the interesting thing, explains Ron Turner, a researcher at the University of Virginia: Not everyone who gets exposed to a cold virus goes on to get sick.
D: Oh, yeah. That's right. For instance, for rhinovirus - the common cold virus - only about 30 percent of contacts in a household will actually develop an infection.
AUBREY: So you could actually be living in the same house, or working in the same office, as someone who's really sick - and you don't get it.
D: That's right. Yeah.
AUBREY: So if people manage to slough off colds, who are they? Or, more importantly, what might they be doing differently? Well, part of the story seems to be sleep. A big study by researcher Sheldon Cohen, at Carnegie Mellon University, found that when people are sleeping poorly, they're significantly more likely to catch a cold.
D: So for hours of sleep, people who slept less than seven hours were 2.9 times more likely to get sick than people who slept eight or more hours.
AUBREY: Cohen says the risk of getting the common cold also seems to be tied to stress. Not that any of us can rid ourselves of all of life's little stressors, but the research suggests it's long durations of stress that wear us down.
D: So kind of chronic, ongoing, enduring problems - being in a bad marriage, having a lousy job - are related to greater risk.
AUBREY: Appalachian State University researcher David Nieman, who's an exercise fanatic, thinks this is a big part of the cold-fighting equation. In his latest study, published this month, he recruited about a thousand volunteers between the ages of 18 and 85. They agreed to complete a daily log of symptoms throughout cold and flu season.
D: See everything from runny nose to sore throat to coughing to fever, headaches - all of those symptoms are listed, and then they rated the severity.
AUBREY: Nieman says what he found really validated his hunch. The more his participants exercised, the less they reported getting sick.
D: If a person put in five days a week, 20 minutes of aerobic activity or more per session, and that was their typical routine, that group had 40 percent fewer days of illness, compared to those who were putting in less than one day a week of activity.
AUBREY: Nieman is not the first researcher to find this relationship between exercise and colds. A study at the Fred Hutchinson Cancer Research Center in Seattle, that tracked what happens when older, sedentary women start walking five days a week, found similar benefits.
AUBREY: How might this work? How could exercise help the immune system fend off a common cold? David Nieman says no one knows for certain, but he suspects that physical activity helps recruit a bunch of important immune cells that normally camp out in different parts of the body - say, in the bone marrow, the spleen or lymph nodes.
D: These cells come out. They're like the Marine Corps or the Special Forces - that get out there, and poke holes into cells that may have viruses in them. And then the viral count goes down, and they kill the viruses.
AUBREY: Allison Aubrey, NPR News.
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