Abstract
BackgroundRegular physical activity is the prime modality for the prevention of numerous non-communicable diseases and has also been advocated for resilience against COVID-19 and other infectious diseases. However, there is currently no systematic and quantitative evidence synthesis of the association between physical activity and the strength of the immune system.ObjectiveTo examine the association between habitual physical activity and (1) the risk of community-acquired infectious disease, (2) laboratory‐assessed immune parameters, and (3) immune response to vaccination.MethodsWe conducted a systemic review and meta-analysis according to PRISMA guidelines. We searched seven databases (MEDLINE, Embase, Cochrane CENTRAL, Web of Science, CINAHL, PsycINFO, and SportDiscus) up to April 2020 for randomised controlled trials and prospective observational studies were included if they compared groups of adults with different levels of physical activity and reported immune system cell count, the concentration of antibody, risk of clinically diagnosed infections, risk of hospitalisation and mortality due to infectious disease. Studies involving elite athletes were excluded. The quality of the selected studies was critically examined following the Cochrane guidelines using ROB2 and ROBINS_E. Data were pooled using an inverse variance random-effects model.ResultsHigher level of habitual physical activity is associated with a 31% risk reduction (hazard ratio 0.69, 95% CI 0.61–0.78, 6 studies, N = 557,487 individuals) of community-acquired infectious disease and 37% risk reduction (hazard ratio 0.64, 95% CI 0.59–0.70, 4 studies, N = 422,813 individuals) of infectious disease mortality. Physical activity interventions resulted in increased CD4 cell counts (32 cells/µL, 95% CI 7–56 cells/µL, 24 studies, N = 1112 individuals) and salivary immunoglobulin IgA concentration (standardised mean difference 0.756, 95% CI 0.146–1.365, 7 studies, N = 435 individuals) and decreased neutrophil counts (704 cells/µL, 95% CI 68–1340, 6 studies, N = 704 individuals) compared to controls. Antibody concentration after vaccination is higher with an adjunct physical activity programme (standardised mean difference 0.142, 95% CI 0.021–0.262, 6 studies, N = 497 individuals).ConclusionRegular, moderate to vigorous physical activity is associated with reduced risk of community-acquired infectious diseases and infectious disease mortality, enhances the first line of defence of the immune system, and increases the potency of vaccination.Protocol registrationThe original protocol was prospectively registered with PROSPERO (CRD42020178825).
Highlights
Lower respiratory tract infections and pneumonia account for more than 4 million deaths annually and upper respiratory infections rank as the leading incident disease in the world [1]
After eligibility assessment 55 studies consisting of seven observational prospective studies and 48 randomised controlled trials (RCTs) met the inclusion criteria
There was a statistically significant effect of physical activity interventions (ESM Figure S2) compared to control with a pooled lower neutrophil count of 704 cells/μL for N = 305 individuals, but not for monocytes (MD = 18 cells/μL 95% CI [− 18 to 54], p = 0.325, I2 = 50.2%, N = 185 individuals) or NK cells (MD = − 15 cells/μL 95% CI [− 47 to 18], p = 0.378, I2 = 46.5%, N = 461 individuals)
Summary
Lower respiratory tract infections and pneumonia account for more than 4 million deaths annually and upper respiratory infections rank as the leading incident disease in the world [1]. An important approach to containing the recent SARS-CoV-2 (COVID-19) outbreak has been the requirement of communities to remain at home (“lockdown”) thereby reducing social contact and containing the spread of the virus Despite these restrictions, numerous governments underlined the importance of remaining physically active for health and wellbeing [3], and recognised the necessity to allow individuals to leave their home to walk, cycle or run. Conclusion Regular, moderate to vigorous physical activity is associated with reduced risk of community-acquired infectious diseases and infectious disease mortality, enhances the first line of defence of the immune system, and increases the potency of vaccination. Protocol registration The original protocol was prospectively registered with PROSPERO (CRD42020178825)
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