Does regular physical activity support brain blood flow and BDNF signaling in older adults?

Regular physical activity is biologically and clinically relevant to brain health in older adults, but the proposed cerebral-blood-flow and synaptic-plasticity pathways are not equally established.

Clinical and physiological evidence

• In adults aged approximately 60 years and older, exercise consistently modulates circulating BDNF, a neurotrophin implicated in synaptic plasticity. A meta-analysis of 11 long-term trials found higher BDNF after exercise (SMD 0.95, 95% CI 0.35–1.55), although heterogeneity was high (I²=82.8%). A systematic review similarly found increased peripheral BDNF in 5 of 6 trials.
• Cerebral perfusion findings are less consistent. Aerobic-training trials have reported increased frontal or anterior-cingulate resting blood flow, but a 26-week trial found no overall perfusion change, and greater fitness gains were associated with lower global flow. Effects may therefore be regional and influenced by vascular health or baseline fitness rather than uniformly increasing whole-brain flow.
• Functional relevance is plausible: in a small randomized crossover trial of sedentary men aged 60–70, 8 weeks of aerobic training improved executive response latency.

Mechanistic and inactivity evidence

• A single 30-minute moderate walk increased serum BDNF in sedentary older adults, supporting movement as an acute neuroplasticity-relevant stimulus. However, circulating BDNF is not a direct measure of BDNF signaling within the brain or of synaptic plasticity.
• Greater sedentary behavior is generally associated with poorer cognition across 33 studies and has been tentatively linked with lower functional-network connectivity. These findings are predominantly cross-sectional and mixed.
• Brief light-walking breaks during sitting did not alter BDNF in reviewed experiments, and TMS/PAS measures of plasticity show variable, largely non-definitive associations with activity.

Bottom line

• For a 77-year-old man, regular activity is well supported as a modulator of BDNF-related biology and may support region-specific cerebral perfusion; inactivity plausibly reduces beneficial movement-related stimulation, but durable loss of synaptic plasticity has not been directly established.