As a co-author of an international consortium, Professor Tibor Hortobágyi, a researcher at the Department of Kinesiology of the Hungarian University of Sports Science (TF), published an article in the high-impact scientific journal GeroScience.
It is still an exciting and unresolved debate among researchers whether exercise generates new neurons in a critical brain structure that subserves memory in healthily aging adults.
Professor Tibor Hortobágyi, a researcher at the Department of Kinesiology at the Hungarian University of Sports Science (TF) and his co-authors aimed to answer this question.
Healthy, natural aging affects the human brain. The size of the hippocampus, the center of memory, starts to decrease after age 50. This atrophy accelerates after age 60, reaching up to 1.4% per year; memory decline ensues. Hippocampal tissue loss is caused by neuroinflammation, reduced trophic support, oxidative damage, cellular senescence, and misfolded protein aggregation. Hippocampal cells also lose their regenerative ability.
There are no drugs to counteract neuronal loss in the human central nervous system. Researchers in the 1960s examined the possibility that non-pharmacological interventions such exercise training could counteract hippocampal atrophy and reduce memory loss. This idea was based on the observations that neurons in certain parts of the hippocampus in rats were still forming weeks after birth. Environmental enrichment in the form of exercise training indeed suggested that hippocampal neurogenesis could occur in mice. A logical next step was to see if similar neuroplasticity could be induced in humans and counteract age-related hippocampal atrophy by promoting neurogenesis.
Human exercise studies in 2010 suggested that 12 months of aerobic exercise training increased hippocampal size measured with magnetic resonance imaging in healthy older individuals. However, influential studies in 2020s failed to reproduce the initial encouraging data on hippocampal neurogenesis in adult humans and controversy started to grow.
The time has arrived to systematically and statistically examine the effects of exercise training on hippocampal size in healthy adult humans. A large international consortium was convened and meta-analyzed the data from randomized controlled trials examining the effects of aerobic exercise training lasting ≥ 4 weeks on hippocampal volume and cardiorespiratory fitness in cognitively unimpaired, healthy older individuals. Eight studies (n=554 people) conducted aerobic training for 3 to 12 months for 130 minutes per week at moderate-to-vigorous intensity. Indeed, aerobic exercise training failed to improve hippocampal volume (SMD=0.10, 95%CI−0.01 to 0.21, p=0.073) while it moderately improved fitness (SMD=0.30, 95% CI 0.12 to 0.48, p=0.005). Sophisticated meta-regression revealed that there was no association between changes in hippocampal volume and fitness (bSE=0.05, SE=0.51, p=0.923). While biologically it might still be plausible to induce hippocampal plasticity by exercise, methodological limitations across the included studies might have masked the lack of effects observed by the meta-synthesis.
Guilherme Moraes Balbim, Nárlon Cássio Boa Sorte Silva, Lisanne Ten Brinke, Ryan S Falck, Tibor Hortobágyi, Urs Granacher, Kirk I Erickson, Rebeca Hernández-Gamboa, Teresa Liu-Ambrose: Aerobic exercise training effects on hippocampal volume in healthy older individuals: a meta-analysis of randomized controlled trials. GeroScience 46:2755–2764, 2024, IF: 5.3.
