1. Exercise May Block Colds
Being fit -- or at least a perception of being fit -- appears to be associated with a reduction in upper respiratory tract infections, researchers found.
During a 12-week period, individuals who said they exercised at least five days a week had 43% fewer days with an upper respiratory tract infection than those who exercised no more than one day a week (P<0.05), according to David Nieman, DrPH, of Appalachian State University in Kannapolis, N.C., and colleagues.
Similarly, those who rated themselves as highly fit had 46% fewer days with a respiratory infection than those who reported low fitness (P<0.05), the researchers reported online in the British Journal of Sports Medicine.
The findings are consistent with previous epidemiologic and randomized studies, they wrote. Although the underlying mechanism remains unclear, the relationship might be explained by the effect of exercise on the body's immune response.
"Each aerobic exercise bout causes a transient increase in the recirculation of immunoglobulins and neutrophils and natural killer cells, two cells involved in innate immune defenses. Animal data indicate that lung macrophages play an important role in mediating the beneficial effects of moderate exercise on lowered susceptibility to infection," Nieman and his colleagues wrote.
"Stress hormones, which can suppress immunity, and pro- and anti-inflammatory cytokines, indicative of intense metabolic activity, are not elevated during moderate aerobic exercise," they continued.
"Although the immune system returns to pre-exercise levels within a few hours after the exercise session is over, each session may improve immunosurveillance against pathogens that reduce overall upper respiratory tract infection incidence and symptomatology."
The researchers followed 1,002 adults up to age 85 during two 12-week periods in 2008; half participated in the fall and half participated in the winter.
Nieman and his colleagues captured the effects of the common cold using the Wisconsin Upper Respiratory Symptom Survey, a reliable and valid daily logging system.
The participants reported how many days they exercised during their leisure time per week and rated their physical fitness on a 10-point Likert scale. They were then divided into tertiles based on their responses.
After adjustment for age, sex, years of education, marital status, mental stress level, body mass index, and fruit intake, individuals who reported exercising at least five days a week spent significantly fewer days, on average, with an upper respiratory tract infection, compared with those who exercised the least (4.41 versus 8.18 days, P<0.05).
A similar difference was observed for the high versus low fitness tertiles (4.89 versus 8.60 days, P<0.05).
In addition to the number of days spent with an upper respiratory tract infection, the severity and symptomatology of such infections was reduced as well, by 32% to 41% between the high versus low aerobic activity and physical fitness tertiles (P<0.05 for all). There were also significant reductions in the middle tertiles.
In a model looking at perceived fitness level, several factors were associated with fewer days spent with an upper respiratory tract infection, including older age, high or medium fitness level, lower education, being married or male, having high versus low BMI, and eating three or more servings of fruit per day (P<0.05 for all).
With the exception of fruit intake, the same factors were significant in a model of exercise frequency as well.
Nieman and his colleagues acknowledged that the study was limited by the lack of adjustment for all potential confounders -- in particular, the study did not adjust for exposure to pathogens at work and in the home.
2. Mindfulness Training:
Dr. Bruce Barrett and 14 co-authors from the University of Wisconsin reported in the Annals of Family Medicine in July, 2012, a prospective, randomized, controlled trial to test whether an 8-week training program in mindfulness meditation or an 8-week training program in moderate intensity sustained exercise would differ from an observational control group at preventing acute respiratory infections (ARIs).
One hundred forty nine community-recruited adults, mostly white females, all over the age of 50, completed the trial. The investigators measured the incidence, duration, and severity of ARIs during a single cold and influenza season.
There were 27, 26, and 40 episodes of 257, 241, and 453 total days of illness in the meditation, exercise, and control groups, respectively.
Mean global severity scores were 144 for meditation, 248 for exercise and 358 for the control group.
There were only 16 ARI related days off work in the meditation group but 32 in the exercise group and 67 days of work missed by the control group.
These are statistically and clinically significant differences. This study was funded by the National Institutes of Health.
Obviously, there needs to be another study to confirm these dramatic findings.
This paper was considered important, relevant, and strong enough to be selected by the BMJEvidence Centre at prestigious McMaster University for its Evidence Updates series.
Yoga is a way to do mindful meditation during moderate intensity sustained exercise, an efficient use of time combining the benefits of both approaches described above.