Impact of aerobic exercise on immune components across healthy and diseased populations: A systematic review and meta-analysis of randomized controlled trials.

Background: Aerobic exercise may improve immune component quantities in healthy and diseased populations, but its effects across different health conditions and immune systems remain unclear. This review examined its impact on immune components in both populations. Methods: A search in June 2025 across four databases included randomized controlled studies on aerobic exercise's effects on immune components in adults. Data (M ± SD) were extracted and converted to standardized mean difference (SMD) using random-effect meta-analysis. Results: Seventeen studies (502 participants) were included. The meta-analysis results showed long-term aerobic exercise increased T-cell counts in diseased individuals (p < 0.05) but not in healthy ones (p > 0.05). It significantly reduced IgA levels in healthy participants compared to non-exercising controls (p < 0.05), potentially counteracting natural temporal increases observed in sedentary populations, without affecting IgG, IgM, leukocytes, neutrophils, or monocytes in either group (p > 0.05). Single-pass exercise did not alter leukocytes, lymphocytes, CD3+, or NK cells in healthy participants (p > 0.05). Conclusions: Long-term aerobic exercise primarily affects adaptive immune components, benefiting individuals with unstable immune conditions. Single-pass exercise has no effect on healthy populations, making long-term interventions more suitable for improving adaptive immunity in unstable immune states. Systematic review registration: www.crd.york.ac.uk/PROSPERO/, identifier: CRD42024546696.