Meeting weekly exercise guidelines was associated with lower pneumonia and influenza mortality, a longitudinal study of U.S. adults showed.

People who met both aerobic physical activity and muscle-strengthening activity guidelines had a 48% lower adjusted risk for pneumonia and influenza death over a median of 9.2 years of follow-up compared with those who met neither (HR 0.52, 95% CI 0.39-0.68), reported Bryant Webber, MD, MPH, of the Division of Nutrition, Physical Activity, and Obesity at the CDC in Atlanta, and colleagues.

“Considering the plausible biological mechanisms and the consistency with previous studies, this protective association may warrant additional clinical and public health efforts to decrease the prevalence of aerobic inactivity and inadequate [muscle-strengthening activity],” the researchers wrote in the British Journal of Sports Medicine.

But the researchers also found a benefit with aerobic activity at levels below guideline recommendations, and a potential harm at the highest levels of strength training, according to their findings.

Guidelines from the Department of Health and Human Services advise at least 150 minutes of moderate-intensity equivalent aerobic physical activity per week, along with two or more episodes of strength training.

Adults engaging in 10 to 149 minutes of moderate- to-vigorous physical activity weekly saw a significant 21% lower risk of pneumonia and influenza death compared with people with no activity. This benefit peaked with a 50% risk reduction for those with 301 to 600 minutes of weekly activity, with no further reduced risk for those engaging in more than 600 minutes of activity.

Participants who reported two episodes of muscle-strengthening activities per week had a 47% lower risk of influenza and pneumonia mortality compared with those who did less than two. However, engaging in seven or more episodes per week was tied to a 41% higher risk of mortality.

About half of the more than 500,000 participants (51%) in the study met neither weekly target, while only 19% met both.

Overall, those who met the aerobic guidelines had a 36% lower adjusted mortality risk from influenza and pneumonia compared with people with no activity (HR 0.64, 95% CI 0.54-0.76), while meeting the muscle-strengthening guidelines was not associated with a significant difference in mortality risk.

Webber and team noted that their findings for reduced mortality are likely due to the fact that exercise is tied to the improvement of several health conditions, including a strengthened immune response.

“Physical activity is associated with lower incidence of several comorbidities, including stroke and coronary heart disease, which increase the mortality risk among adults hospitalized with community-acquired pneumonia,” they wrote. “Clinical trials have demonstrated that aerobic training programs improve expectoration in persons with cystic fibrosis and peak oxygen uptake in persons with COPD.”

The study’s results build on previous findings showing that exercise proved beneficial following pulmonary embolism, and may have cardiorespiratory benefits for patients undergoing chemotherapy.

For this cohort study, Webber and colleagues included 577,909 adults who participated in the National Health Interview Survey from 1998 to 2018 and were followed for a median of 9.23 years; 52.2% were women, and 69.2% were white.

Participants were classified into five volume-based categories of self-reported aerobic and muscle-strengthening activity.

During follow-up, 81,431 deaths were observed, with 1,516 deaths from pneumonia and influenza.

Webber and team noted that physical activity was measured in intervals of 10 minutes or more, meaning shorter episodes were not included. This, paired with potential gaps in mortality data, the chance that underlying health conditions may have caused changes in an individual’s physical activity, and other factors, may have affected the study’s results.

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