STEVE INSKEEP, HOST:
Do you ever wonder why some people get sick and others seem almost immune? Evidence going back decades has shown that people who are stressed or fatigued are more likely to catch a cold. Now a study finds that your performance on quick brain quizzes may help to predict how vulnerable you are to getting sick from a virus. NPR's Allison Aubrey reports.
ALLISON AUBREY, BYLINE: Our health care system tends to separate mental health and physical health, but, of course, they're inextricably linked. Being stressed out can mess with our immune systems. And researchers have come up with clever ways to study this. For instance, in one study, scientists exposed hundreds of healthy people by injecting a common cold virus into their noses. Then they waited to see who got sick. It turned out the people who had high levels of stress were more than twice as likely to catch a cold compared to people with low stress. Murali Doraiswamy is a professor of psychiatry and behavioral sciences at Duke University School of Medicine.
MURALI DORAISWAMY: It's well known that if you're under periods of intense stress, you are more likely more susceptible to catching viral infections.
AUBREY: It's also known that a lack of sleep and a lack of physical activity can make us vulnerable to infection, too. Now Professor Doraiswamy and colleagues have set out to determine whether changes in a person's cognitive performance, such as our ability to stay focused, problem solve and think quickly, may also signal vulnerability. To figure this out, they recruited healthy people who agreed to have the virus put up their noses and also take brain quizzes multiple times a day for several days. One game was kind of like a timed crossword puzzle - another quiz, scrambled numbers and letters.
DORAISWAMY: They're all the time tests - so reaction time, just how quickly can you press a button to solve something?
AUBREY: The participants' speed and accuracy was used to gauge their mental sharpness. In addition, the severity of their colds was measured by how much virus they shed.
DORAISWAMY: We were able to explicitly quantify how many millions of particles of virus they were actually shedding from their body at each time point.
AUBREY: When all was said and done, there was a wide range of performance on the cognitive test, says co-author Alfred Hero, a professor of biomedical engineering at the University of Michigan.
ALFRED HERO: Some subjects were very consistent, and on the other extreme, we had subjects who might go from doing quite well in the morning to doing very, very poorly later on in the day.
AUBREY: And it turned out people who seesawed between good and bad performance were more likely to get sicker with more severe symptoms.
Here's Murali Doraiswamy again.
DORAISWAMY: What we found was that the people who showed high variability also had greater shedding and greater severity of symptoms.
AUBREY: It's not clear why the variability in performance on tests would be predictive. Physician Ron Turner, a longtime common cold and immunity researcher at the University of Virginia, says his hunch is that this is a marker for other things happening in a person's life.
RON TURNER: It's very likely, in my opinion, that the variability in cognitive function is a stand-in or an association with other things, whether that's stress or whether that's lack of sleep.
AUBREY: Which takes us back to where we started. Both are known risk factors. So perhaps subtle changes in cognitive performance could serve as a broader catchall to predict vulnerability before we're even aware of it. Of course, in real life you can't ask people to do a bunch of brain games all day, but there is a more passive way to measure cognitive changes. And Alfred Hero says our smartphones and laptops can already capture metrics that are reflective of reaction time and mental sharpness.
HERO: How quickly one writes an email, how quickly one clicks on a particular link, how much one goes back and forth in a Google search - all of these things that are much better suited to a continual type of measurement.
AUBREY: The study was funded by the Defense Department to explore the prevention of illness for soldiers in group living quarters, but it could be developed for a broader audience. It's possible one day in the future, just as your smartphone tells you it's time to leave for an appointment to be on time, it could alert you that you're at risk of a virus.
Allison Aubrey, NPR News.
(SOUNDBITE OF MASTON'S "LES MONSTRES") Transcript provided by NPR, Copyright NPR.
