The Impact of Different Types of Exercise Training on Peripheral Blood Brain-Derived Neurotrophic Factor Concentrations in Older Adults: A Meta-Analysis

Background As the prevalence of neurodegenerative diseases (such as dementia) continues to increase due to population aging, it is mandatory to understand the role of exercise for maintaining/improving brain health. Objectives To analyse the impact of aerobic, strength and combined aerobic/strength exercise training on peripheral brain-derived neurotrophic factor (BDNF) concentrations in older adults (minimum age 60 years). Methods This meta-analysis adhered to PRISMA guidelines. Inclusion criteria were: (i) studies with subjects aged >= 60 years, (ii) completing a single exercise bout or an exercise programme, with (iii) measurements of blood BDNF in the periphery; (iv) with comparison between (a) an intervention and control group or (b) two intervention groups, or (c) pre- and post-measurements of an exercise intervention without control group. Studies with specific interest in known chronic co-morbidities or brain diseases affecting the peripheral and/or central nervous system, except for dementia, were excluded. Results In general, peripheral blood BDNF concentrations increased significantly after a single aerobic/strength exercise bout (Z = 2.21, P = 0.03) as well as after an exercise programme (Z = 4.72, P < 0.001). However, when comparing the different types of exercise within these programmes, the increase in the peripheral BDNF concentrations was significant after strength training (Z = 2.94, P = 0.003) and combined aerobic/strength training (Z = 3.03, P = 0.002) but not after (low-to-moderate intense) aerobic exercise training (Z = 0.82, P = 0.41). Conclusions Based on current evidence, to increase the peripheral blood BDNF concentrations in older adults, strength training and combined aerobic/strength training is effective. More studies are needed to examine the impact of aerobic exercise training.