There may not be a cure for the common cold, but people who exercise regularly seem to have fewer and milder colds, a new study suggests.
In the United States, adults can expect to catch a cold two to four times a year, and children can expect to get six to 10 colds annually. All these colds sap about $40 billion from the U.S. economy in direct and indirect costs, the study authors estimate. But exercise may be an inexpensive way to put a dent in those statistics, the study says.
"The physically active always brag that they're sick less than sedentary people," said lead researcher David C. Nieman, director of the Human Performance Laboratory at the Appalachian State University, North Carolina Research Campus, in Kannapolis, N.C. "Indeed, this boast of active people that they are sick less often is really true."
The report is published in the Nov.1 online edition of the British Journal of Sports Medicine.
For the study, the researchers collected data on 1,002 men and women from ages 18 to 85. Over 12 weeks in the fall and winter of 2008, the researchers tracked the number of upper respiratory tract infections the participants suffered. In addition, all the participants reported how much and what kinds of aerobic exercise they did weekly, and rated their fitness levels using a 10-point system. They were also quizzed about their lifestyle, dietary patterns and stressful events, all of which can affect the immune system.
The researchers found that the frequency of colds among people who exercised five or more days a week was up to 46 percent less than those who were largely sedentary - that is, who exercised only one day or less of the week.
In addition, the number of days people suffered cold symptoms was 41 percent lower among those who were physically active on five or more days of the week, compared to the largely sedentary group. The group that felt the fittest also experienced 34 percent fewer days of cold symptoms than those were felt the least fit.
Moreover, colds also appeared to be less severe for those in better shape. Among those who felt the fittest, the severity of symptoms dropped by 32 percent and by 41 percent among those who exercised most, the researchers note.
One limitation of the study was a lack of adjustment for all variables that might affect the outcome, such as exposure to cold germs at work or from children in the home, the researchers noted. Nieman said one explanation for the finding could be that exercise activates the immune system at a higher rate than normal and causes immune cells to attack viruses.