The Effects of Acute and Chronic Exercise on Brain Derived Neurotrophic Factor and Cognitive Performance in Mild Cognitive Impairment

Abstract

Introduction: Brain Derived Neurotrophic Factor (BDNF) is a neurotrophin that supports neural survival, growth and synaptic plasticity and is upregulated through exercise. While the exact neuronal mechanisms underlying the exercise-cognitive relationship have not been fully elucidated, recent evidence postulates BDNF as a mediator of this relationship. Increased BDNF in response to exercise has demonstrated simultaneous improvements in cognitive performance in healthy young cohorts, yet little is known about the effects of exercise on serum BDNF (sBDNF) concentration and cognitive performance in a Mild Cognitive Impairment (MCI) population. Objective: To investigate sBDNF and cognitive change in response to acute and chronic exercise in individuals with MCI Methods: Blood sampling and cognitive measures (tests of visuospatial learning and memory, sustained attention and executive function) were collected pre and post defined exercise conditions of varying modality, duration and intensity during participation in a 12-month exercise intervention study (aerobic v balance and toning v control). Results: 62 participants (female 53.2%, mean age 70.5 +/- 6.3 years) with MCI were recruited. Results demonstrate that a short bout of high intensity exercise increased sBDNF concentration from 4564.61 pg/mL (+/- 5737.23) to 5173.27 pg/mL (+/- 5997.54) and this differed significantly compared to a resting control condition (4593.74 +/- 9558.29 pg/mL to 3974.66 +/- 3668.22 pg/mL), (p=0.024, ES=0.3). Furthermore, following 6 weeks of structured exercise training, basal sBDNF concentration increased significantly in the aerobic group from 1340.81 pg/mL (+/- 593.53) to 32464.69 pg/mL (+/- 6567.70) (p = 0.000), and in the balance and toning group from 1261.51 pg/mL (+/- 469.40) to 34418.94 pg/mL (+/- 5757.52) (p= 0.000), but this did not differ between groups. Despite BDNF change, cognitive performance did not improve following acute or chronic exercise. Overall adherence rates to the prescribed 12-month exercise intervention were poor and a 12 month exercise intervention did not impact BDNF or cognition. Episodic memory remained largely stable over a one year period and this did not differ between study intervention groups. Conclusion: A single session of high intensity acute aerobic exercise and 6 weeks of structured aerobic or balance and toning exercise training increases peripheral sBDNF concentration in an MCI population. However, changes in BDNF were not associated with an improvement in cognitive performance in this cohort. Future exercise intervention studies need to need to develop suitable adherence supports to enable active exercise participation in cognitively impaired populations.