Does regular exercise reduce the occurrence, severity, or duration of acute respiratory tract infections?
For adults, regular exercise may reduce the overall severity of acute respiratory tract infections and the number of days with symptoms, but there is no evidence that exercise reduces the overall occurrence or duration of these infections.1 (Strength of Recommendation: B, based on inconsistent or limited-quality patient-oriented evidence.)
Acute respiratory tract infections (i.e., infections of the respiratory tract lasting less than 30 days) are a common cause of morbidity each year.2 In 2016 in the United States, 9.6% of all medical office visits were for respiratory diseases.3 A 2015 Cochrane review of 11 trials involving 904 adults did not determine whether exercise could affect the occurrence, severity, or duration of acute respiratory tract infections and called for larger, higher-quality studies.4
For this updated review, the authors added three new trials for a total of 1,377 adults; nine trials were from the United States and the remainder were from Brazil, Canada, Portugal, Spain, and Turkey.1 Participants were 18 to 85 years of age. Study duration ranged from seven days to 12 months, and the most common intervention was supervised aerobic exercise for 30 to 45 minutes per session for three to five days each week. All studies compared exercise with no exercise. The review authors relied on the definition of acute respiratory tract infections used by the trial authors. The studies in this review were assessed as being at low risk of reporting bias; low, unclear, or high risk of attrition bias; unclear risk of selection bias; and high risk of performance and detection bias.
Low-certainty evidence demonstrated that aerobic exercise vs. no exercise does not reduce the number of acute respiratory tract infection episodes per year or the proportion of individuals who will experience at least one acute respiratory tract infection over 12 to 52 weeks of follow-up.
The effect of exercise vs. no exercise on severity of acute respiratory tract infection symptoms was measured in two studies.5,6 The studies calculated global severity using scores on the Wisconsin Upper Respiratory Symptom Survey (WURSS), a validated tool used to determine the severity of upper respiratory tract infections in study participants.7 When combined, these two studies found that over eight weeks of follow-up, participants who exercised scored a mean total of 236 points on the WURSS tool, whereas those who did not scored a mean total of 342 points, for a mean difference of 106 points.5,6 This finding was rated low certainty because of a lack of blinding and the wide CIs for the results.
The reviewers also found that exercise reduced the overall number of symptomatic days over 12 weeks of follow-up (mean difference = −2.24 days; 95% CI, −3.50 to −0.98), but they did not note a reduction in symptomatic days per illness episode; these findings were rated low certainty because of the risk of selection bias and inconsistency of results between studies. Exercise did not impact quality of life or disease cost and did not seem to cause more exercise-related injury. The evidence supporting these conclusions remains of low certainty, and future high-quality studies are needed to provide further clarity on the benefits of exercise for acute respiratory tract infections.
The practice recommendations in this activity are available at http://www.cochrane.org/CD010596.