INDIANAPOLIS — The American College of Sports Medicine (ACSM) has released a study that sheds new light on the effect of physical activity on the risk of catching colds; the results were published in the August 2002 issue of Medicine & Science in Sports & Exercise®. It is well known that extreme physical exertion increases the risk of developing an upper respiratory tract infection, but previously, little data existed that described differences in the risk of infection between low and moderate levels of physical activity. Researchers from the University of South Carolina and the University of Massachusetts examined rates of upper respiratory tract infections (URTI) among inactive and moderately active middle-aged adults, and fund that moderately active individuals reported fewer infections.

"Because the average adult suffers two to five colds a year, resulting in missed work and visits to their doctor, we believed any information we could provide about modifiable risk factors for colds would be valuable," said Charles E. Matthews, Ph.D., lead researcher on the study. "This study provides evidence that regular participation in physical activity reduces the risk of infection by nearly 25 percent, which in turn may reduce health care costs and increase worker productivity." The researchers examined the physical activity — URTI association using data from the Massachusetts-based Seasonal Variation of Blood Cholesterol study.

The Seasonal Variation in Cholesterol study was designed to quantify the magnitude and timing of seasonal changes in blood lipids and to identify the major factors that contribute to these changes. It followed 641 healthy men and women between 20 and 70 years of age for one year. Data collected included the assessment of physical activity, diet, psychosocial factors (depression, anxiety), health habits (smoking, alcohol), as well as demographic characteristics (age, gender, education, family structure). Clinic visits every three months provided the setting for reporting the number of colds, flu, or allergies. The incidence of URTI was calculated from the number of colds reported during the period, excluding reports of flu and allergy. Physical activity was assessed by a series of 15 24-hour physical activity recalls over the year (three recalls every three months).

After collecting and analyzing the data, the researchers found that roughly 40 percent of the group reported colds in the fall and winter and ten percent reported colds during summer. They found that moderate levels of activity reduced the annual risk for URTI by 23 percent relative to lower levels of activity, after controlling for a number of other factors. In the fall of the year, moderate levels of activity reduced risk by about 30 percent. While these results reflect the effect of moderate and vigorous activity combined, the researchers note that most individuals reached higher activity levels by participating in moderate intensity activities at home, at work or during their leisure time.

The researchers noted that because this was an observational study and self-reports of illness and physical activity were used, obvious limitations apply; but these data are consistent with other research, and they provide compelling evidence that participation in regular physical activity reduces the incidence of upper respiratory tract infection in adults.

Note: The American College of Sports Medicine is the largest sports medicine and exercise science organization in the world. More than 18,000 International, National and Regional members are dedicated to promoting and integrating scientific research, education and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health and quality of life.

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