Exercise and the Aging Brain: How Physical Activity Helps Preserve the Hippocampus and Memory
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The hippocampus, a brain region essential for learning and memory, naturally shrinks with age, contributing to age-related cognitive decline.
A landmark 2011 study by Erickson et al. found that one year of aerobic exercise increased hippocampal volume by approximately 2% in older adults, while the control group experienced a decline of about 1.4%.
Participants who engaged in aerobic exercise also improved their spatial memory, linking changes in brain structure to cognitive benefits.
Exercise may protect the hippocampus through several mechanisms, including increased BDNF signaling, neuroplasticity, improved blood flow, and healthier neural connections.
A subsequent meta-analysis found that exercise interventions can help preserve hippocampal volume, with benefits particularly evident in adults aged 65 and older.
The takeaway: Regular, sustained physical activity—ideally working toward 150 minutes of moderate-intensity aerobic exercise weekly—may help preserve brain health, memory, and cognitive function as we age.
Your brain changes with age, but the loss of memory and cognitive function is not an inevitable part of growing older. Research suggests that regular aerobic exercise may help preserve, and even increase the volume of, an important brain structure responsible for learning and memory- the Hippocampus.
The hippocampus: A small structure with a big responsibility
Have you ever walked into a room and forgotten why you went there? Struggled to recall a name that was once familiar? Or noticed that learning something new seems to take longer than it used to?
Occasional forgetfulness can be a normal part of aging. However, these experiences highlight the importance of protecting the brain systems responsible for memory and learning.
One of the most important structures involved in these functions is the hippocampus, a seahorse-shaped region located deep within the temporal lobes of the brain. It plays a central role in forming new memories, consolidating information, and supporting spatial navigation.
Unfortunately, the hippocampus is vulnerable to aging. As we grow older, its volume tends to decrease, and this structural change is associated with age-related memory difficulties and an increased risk of cognitive impairment.
But here is the encouraging news: the aging brain retains a remarkable capacity for adaptation. One of the most accessible ways to support this capacity may be something many of us underestimate—regular physical exercise.
A landmark study: Can exercise actually increase brain volume?
In 2011, Kirk I. Erickson and colleagues published an influential study in the Proceedings of the National Academy of Sciences (PNAS) titled Exercise Training Increases Size of Hippocampus and Improves Memory. The researchers investigated whether aerobic exercise could counteract age-related hippocampal shrinkage and improve memory in older adults.
The study provided compelling evidence that the aging brain remains modifiable, even later in life.
What did the researchers do?
The investigators randomly assigned 120 older adults without dementia to one of two groups:
Aerobic exercise group: Participants engaged in a year-long program of moderate-intensity aerobic exercise, primarily walking.
Control group: Participants took part in stretching and toning exercises.
The researchers used magnetic resonance imaging (MRI) to measure brain volume before the intervention, at six months, and after one year. They also assessed participants' aerobic fitness and memory performance.
This design allowed the researchers to examine whether aerobic exercise was associated with measurable changes in brain structure and cognitive function.
What did they discover?
1. Aerobic exercise increased hippocampal volume.
After one year, the aerobic exercise group demonstrated an approximately 2% increase in hippocampal volume. Specifically, the left hippocampus increased by 2.12%, and the right increased by 1.97%.
In contrast, the stretching control group experienced a decline of approximately 1.4% in both hippocampi over the same period.
The researchers estimated that the exercise-associated increase was equivalent to reversing approximately one to two years of age-related hippocampal volume loss in this population.
This finding is particularly important because it challenges the assumption that age-related brain shrinkage is necessarily irreversible.
2. Exercise improved memory performance.
The benefits extended beyond MRI measurements. Participants in the aerobic exercise group also demonstrated improvements in spatial memory, which helps us learn and remember locations and navigate our surroundings.
Importantly, participants who experienced greater increases in hippocampal volume tended to show greater improvements in memory. This relationship suggests that the structural changes may have functional significance rather than representing merely an anatomical difference.
3. The benefits were region-specific.
Exercise did not enlarge every brain structure examined. The most notable changes occurred in the anterior hippocampus, while the posterior hippocampus showed little change. The researchers did not find comparable significant intervention effects in the thalamus or caudate nucleus.
This specificity suggests that physical activity may influence particular neural systems rather than uniformly increasing brain volume.
4. Better fitness was associated with protection against volume loss.
The researchers also found that higher aerobic fitness was associated with a more favorable hippocampal outcome. Participants' fitness levels and changes in brain volume were linked, supporting the possibility that cardiovascular fitness contributes to maintaining brain health as we age.
Reference: Erickson KI, et al. Proc Natl Acad Sci U S A. 2011;108(7):3017–3022. doi:10.1073/pnas.1015950108.
Why does exercise benefit the hippocampus?
The study's findings become even more interesting when we consider the biological mechanisms that may explain them.
1. Brain-derived neurotrophic factor: Supporting the brain's ability to adapt
One important molecule is brain-derived neurotrophic factor (BDNF), a protein that supports neuronal health, synaptic plasticity, and memory formation.
BDNF helps neurons maintain and strengthen their connections, making it important for learning and the formation of lasting memories.
In the Erickson study, increases in serum BDNF were associated with increases in anterior hippocampal volume. Although this does not establish that BDNF directly caused the volume changes, it provides a plausible biological link between exercise and brain plasticity.
Research suggests that aerobic exercise can influence BDNF signaling, potentially helping the brain adapt to experience and maintain the neural connections needed for memory.
2. Neuroplasticity: The brain retains the ability to change
For many years, the adult brain was viewed as relatively fixed, particularly in later life. We now understand that the brain can continue to change in response to experience.
This capacity, known as neuroplasticity, includes strengthening existing synapses, modifying neural networks, and, under certain conditions, generating new neurons.
The hippocampus is particularly important in this discussion because the dentate gyrus, a subregion involved in learning and memory, is associated with adult neurogenesis in animal research. The extent and functional significance of adult hippocampal neurogenesis in humans remain subjects of scientific debate.
The increase in hippocampal volume observed in the exercise study could reflect several biological changes, including altered dendritic complexity, synaptic remodeling, vascular changes, or other tissue adaptations. MRI cannot determine which of these mechanisms is responsible.
The central message remains encouraging: the aging brain can retain the capacity for meaningful structural and functional adaptation.
3. Improved blood flow and vascular health
Aerobic exercise strengthens the cardiovascular system and supports healthy circulation. The brain depends on a continuous supply of oxygen and nutrients to sustain its activity.
Exercise can improve vascular function and cerebral perfusion, potentially supporting the metabolic needs of neurons and the maintenance of healthy brain tissue.
Because the hippocampus is metabolically active and vulnerable to age-related changes, maintaining cardiovascular health may be one important component of preserving its function.
4. Multiple pathways work together
Exercise does not act through a single molecule or mechanism. Its potential benefits for the aging brain likely reflect the combined effects of neurotrophic signaling, vascular adaptation, metabolic regulation, and changes in neural connectivity.
These mechanisms may help explain why a behavior that benefits the heart and muscles can also influence memory and brain structure.
How much exercise does the aging brain need?
The encouraging message is that protecting brain health does not necessarily require an extreme workout routine. Consistency over time may matter more than intensity alone.
A subsequent meta-analysis by Wilckens and colleagues, published in Hippocampus in 2021, examined 23 exercise interventions across 22 studies involving 1,204 participants. The researchers found a significant overall positive effect of exercise on hippocampal volume. Benefits were particularly evident in adults aged 65 and older and in interventions lasting longer than 24 weeks. The findings support the potential value of sustained exercise, although results across studies have not been entirely consistent. Read the meta-analysis.
For most adults, a practical starting point is:
Aerobic exercise: Aim toward 150 minutes per week of moderate-intensity activity, such as brisk walking, swimming, or cycling, as tolerated.
Strength training: Include muscle-strengthening activities at least twice weekly to support mobility, independence, and overall health.
Consistency: Start at a manageable level and build gradually. Benefits may require months of sustained activity rather than a few isolated workouts.
Adaptation: Choose activities that suit your current fitness, balance, joint health, and medical circumstances. Even short bouts of movement are worthwhile if you are starting from a sedentary baseline.
The 150-minute target is consistent with general physical activity guidance for adults; it is not a proven minimum dose specifically required to increase hippocampal volume. The optimal exercise prescription for preserving brain structure continues to be investigated.
If you have cardiovascular disease, significant balance difficulties, or other medical limitations, consult a healthcare professional about a safe exercise plan.
Why starting earlier—and continuing later—matters
Although the study by Erickson and colleagues focused on older adults, the implications extend across the lifespan.
Physical activity in midlife may help establish and maintain cardiovascular fitness before age-related changes become more pronounced. In later life, exercise may help counter some of the biological changes associated with aging and support the preservation of memory and independence.
Most importantly, it is not too late to begin.
The participants in the landmark study were already in late adulthood, yet the exercise group experienced measurable improvements in hippocampal volume and spatial memory. This finding challenges the belief that meaningful brain-health benefits are available only to younger people.
Exercise should not be presented as a guarantee against Alzheimer's disease or dementia. Cognitive decline is influenced by multiple factors, including genetics, vascular health, sleep, medical conditions, and lifestyle. Nevertheless, physical activity is an accessible and evidence-supported component of a broader strategy to maintain health as we age.
The bigger picture: Exercise is an investment in your future brain
We often think of exercise in terms of weight management, muscle strength, or cardiovascular fitness. These are important benefits, but the brain deserves a place in the conversation.
Every walk, cycling session, swim, or other suitable physical activity is an opportunity to support the systems that sustain our ability to learn, remember, and navigate the world.
The research by Erickson and colleagues offers a particularly powerful message: the brain is not simply a passive victim of aging. It retains a capacity for adaptation, and physical activity may help us make the most of it.
We cannot stop the passage of time. We cannot guarantee that we will never experience memory difficulties. But we can take meaningful steps to support our brain health.
Perhaps one of the most important reasons to exercise is not how we look in the mirror today, but how we want our brains to function years from now.
Move for your heart. Move for your muscles. And move for your memory.
References
Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proc Natl Acad Sci U S A. 2011;108(7):3017–3022. doi:10.1073/pnas.1015950108. PubMed.
Wilckens KA, Stillman CM, Waiwood AM, et al. Exercise interventions preserve hippocampal volume: A meta-analysis. Hippocampus. 2021;31(3):335–347. doi:10.1002/hipo.23292. PubMed.
Chen FT, Hopman RJ, Huang CJ, et al. The effect of exercise training on brain structure and function in older adults: A systematic review based on evidence from randomized control trials. J Clin Med. 2020;9(4):914. doi:10.3390/jcm9040914. PubMed.
