The role of physical exercise in modulating peripheral inflammatory and neurotrophic biomarkers in older adults: A systematic review and meta-analysis

•Little is known on how exercises that improve cognition alter blood biomarkers.•We conducted a systematic review and meta-analysis on the literature.•Included studies conducted exercise interventions for cognition in older adults.•Aerobic and multimodal training either increased or maintained BDNF concentrations.•Resistance training either increased or maintained IGF-1 concentrations. Physiological cascades of neurotrophic factors and inflammatory cytokines may mediate the exercise-induced amelioration of cognition in older adults. However, there is limited understanding on how different exercise modalities improving cognition alter biomarkers. Our aim was to evaluate the effects of different exercise modalities on blood biomarker concentrations in cognitive clinical trials of older adults. A systematic review (SR) and meta-analysis (MA) were performed using the databases PubMed, EMBASE, and SCOPUS. After exclusions, 17 trials with 18 distinct exercise interventions were included. Aerobic training increased (n = 2) or did not significantly change BDNF (n = 5), and resistance training increased (n = 2) or did not significantly change (n = 2) IGF-1. Multimodal training significantly increased (n = 1) or did not change (n = 3) BDNF. Interventions that recruited sex-specific cohorts showed an advantage in males for blood marker concentrations and cognitive performance outcomes (n = 3) compared to females (n = 3). Only one of three interventions decreased concentrations of CRP. Eight studies examining BDNF changes were suited for MA and showed that higher BDNF concentrations were reached post intervention, although not reaching statistical significance (p = .26, I2 = 44 %). Our results suggest that exercise has potential to ameliorate cognitive decline in older adults with divergent, modality-specific, neurotrophic mechanisms.