How do different physical exercise parameters modulate brain-derived neurotrophic factor in healthy and non-healthy adults? A systematic review, meta-analysis and meta-regression

Summary Objectives Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays crucial role on synaptic plasticity, neurogenesis, and neuroprotection. Exercise has been established as capable to increase BDNF level in the elderly, leading to improvement in brain functions, including learning and memory. However, there is no data regarding recommendation protocol that may lead to BDNF increase in this population. Then, we conducted a systematic review and meta-analysis to address this issue. News We searched on nine large electronic databases until September 2018. Articles that evaluated the effect of exercise training on BDNF level were included. Regarding meta-analysis, random effect and meta-regression were conducted. Across twenty-five included studies in meta-analysis ( n  = 2152), we found exercise could lead to significant increase in BDNF level in adults (596.33 pg/ml) (95% CI: 471.76–720.89; P I 2  = 97.5%; n  = 921) comparing to control groups. Interestingly, this increase was independent of age group and health status. Meta-regression analyses found that variables such as age, exercise intensity, session and intervention duration, and exercise modality contribute to heterogeneity in terms of the entire population. Conclusions Respecting study limitations, we suggest based on our results and available evidence, the following FITT-based exercise recommendation to improve BDNF level: Frequency: 2–3 times per week; Intensity: at least 65% of VO 2 max; Type: moderate-intensity continuous training; Time: at least 40 minutes. Also, exercise is more effective at improving the BDNF level in lengthier intervention, and exercise intensity is linearly associated with BDNF changes.