Aerobic physical activity, even at quanitites lower than recommended, was associated with an almost 50% lower risk of death from influenza and pneumonia in a study published in the British Journal of Sports Medicine. Muscle-strengthening exercise displayed a J-shaped relationship with influenza and pneumonia mortality in the study.
The risk of influenza and pneumonia mortality was significantly lower among participants who performed 10-150 minutes per week of leisure-time moderate-to-vigorous physical activity (MVPA), compared with those who performed none. Even though this level is often labeled “insufficient” because it is less than recommended by the WHO and US Department of Health and Human Services, it may still deliver health benefits relative to physical inactivity.
Also, independent of aerobic activity, mortality risk was significantly lower among participants who performed 2 muscle-strengthening activity (MSA) episodes per week compared with those who performed less than 2 episodes per week. On the other hand, it was found that performing 7 or more MSA episodes per week was associated with an increased risk.
This study was conducted because it is known that physical activity plays a role in preventing diseases. It is recommended that adults perform moderate-intensity aerobic physical activity for at least 150 minutes per week, or vigorous-intensity aerobic physical activity for at least 75 minutes each week, or an equivalent combination. Additionally, muscle-strengthening activity of moderate or greater intensity at least 2 times per week is recommended.
“According to the guidelines, these benefits include prevention of dementia, cardiovascular disease and some cancers; improved physical function and mental health; and greater longevity. Regular physical activity may also protect against infection and mortality from infectious diseases,” wrote the study authors.
A nationally representative sample of American adults (aged ≥ 18 years) who participated in the National Health Interview Survey (NHIS) from 1998 to 2019 were followed for mortality through 2019 in this study, which aimed to analyze the association of leisure-time physical activity with mortality from influenza and pneumonia.
Next, researchers classified participants as meeting both physical activity guidelines if they reported at least 150 minutes per week of moderate-intensity equivalent aerobic physical activity and at least 2 episodes per week of muscle-strengthening activity. They were also classified into 5 volume-based categories of self-reported aerobic and muscle-strengthening activity.
Influenza and pneumonia mortality was defined as “having an underlying cause of death with an International Classification of Diseases, 10th Revision code of J09-J18 recorded in the National Death Index.” Mortality risk was evaluated using Cox proportional hazards, adjusting for sociodemographic and lifestyle factors, health conditions and influenza, and pneumococcal vaccination status. The data were analyzed in 2022.
Compared with participants who met neither guideline, those meeting both the aerobic and muscle-strengthening guidelines had a 48% lower adjusted risk of influenza and pneumonia mortality.
Compared with no aerobic activity, performing 10-149, 150-300, 301-600, or more than 600 minutes per week was associated with lower risk (by 21%, 41%, 50%, and 41%, respectively). Performing 2 episodes of muscle-strengthening exercise per week was associated with a 47% lower risk of mortality vs less than 2 episodes per week, but performing 7 or more episodes per week was associated with a 41% higher risk.
There are at least 2 clinical implications that this study offers, according to the authors.
“First, the mortality benefit associated with ‘insufficient’ aerobic physical activity and with 2 MSA episodes/week might provide additional justification for healthcare providers to promote physical activity among their inactive patients,” said the researchers.
“Second, given the increased mortality risk among those reporting ≥7 MSA episodes/week, clinical decision tools related to physical activity screening may want to flag very high levels of MSA, in addition to levels below guidelines,” they added.
This study had some limitations. The data were self-reported, NHIS only inquired about leisure-time physical activity in bouts of 10 or more minutes, data was collected from public-use linked mortality files, and individuals may have altered their physical activity based on underlying conditions.
Still, the authors suggest that guidelines should be updated to reflect the emerging body of evidence that shows an association between physical activity and lower mortality from infectious diseases.
“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 MSA,” concluded the researchers.
Webber BJ, Yun HC, Whitfield GP. Leisure-time physical activity and mortality from influenza and pneumonia: a cohort study of 577909 US adults. Br J Sports Med. Published online May 16, 2023. doi:10.1136/bjsports-2022-106644