When Physical Activity Impacts Alzheimer's

Exploring the effects of sports on memory, scientists from UNIGE have discovered compensatory mechanisms in the brains of young individuals with a genetic risk of developing Alzheimer's disease.


The benefits of physical activity for health are widely recognized, and those for cognitive abilities are increasingly known. However, there could be exceptions.

By studying the effects of sports on the memory of young adults carrying a genetic variation that increases the risk of Alzheimer's disease, neuroscientists from the University of Geneva (UNIGE), in collaboration with the University Hospitals of Geneva (HUG) and the University of Lausanne (UNIL), revealed poorer associative memory in these at-risk individuals, unlike those without this genetic mutation.

These findings, published in the journal Cerebral Cortex, also highlight compensatory brain mechanisms in these young adults, who nonetheless show no clinical symptoms of the disease.

During physical exertion, the body produces small molecules, the endocannabinoids, which trigger a sense of well-being and activate the hippocampus, a part of the brain that plays a crucial role in memory and spatial navigation. Neurons in this cortical area are the first to degenerate during the development of Alzheimer's disease.

Kinga Igloi, a scientific collaborator in the group of Sophie Schwartz, a full professor in the Department of Basic Neurosciences at the Faculty of Medicine and the Geneva Neuroscience Center at UNIGE, studies the effects of physical exercise on memory.

In a previous study, her work showed that a 30-minute session of moderate-intensity sports improved memory abilities.

In the current study, the researchers aimed to determine whether the benefits of sports on memory were also present in young, healthy individuals with an increased genetic risk of developing Alzheimer's disease. These individuals, like 20% of the population, carry a variation of the APOE gene which increases the risk of Alzheimer's disease by three to twelve times, and, if the disease develops, advances its onset by nearly 15 years (around 68 years compared to 84 years for individuals without this mutation).

A notable difference in memory tests

The scientists asked 50 individuals aged 18 to 25 without any cognitive deficits to perform a task that required their declarative memory, which corresponds to the memory of personal events (who I met yesterday) or general knowledge (which city is the capital of Switzerland), and which depends on the hippocampus.


The volunteers had to learn series of images, then either do 30 minutes of stationary cycling at a moderate speed or rest for 30 minutes. Finally, their memory was tested by asking them to recall the order in which the images were presented.

Half of the volunteers carried the risk variant of the APOE gene, and the other half formed the control group. Brain images were taken by MRI during learning and recall phases to visualize the intensity of hippocampal activation. Additionally, blood samples were taken to measure endocannabinoid levels.

"To our surprise, the at-risk group performed worse than the control group in this memory task, whether after a cycling session or a rest phase, unlike the control group," explains Kinga Igloi.

Cerebral overcompensation

In the control group, improved performance after physical exercise was accompanied by an increase in hippocampal activation - the brain region crucial for memory - and a rise in endocannabinoid levels in the blood.

Conversely, in the at-risk group, MRI measures revealed hyperactivation of hippocampal neurons under all test conditions. "This observation suggests the presence of physiological adaptation or compensation mechanisms. Thus, the brains of these individuals would recruit hippocampal regions more intensively to achieve memory scores similar to or lower than those of the control group," says Sophie Schwartz.

The scientists are now continuing their behavioral and brain imaging studies to understand if different tasks, involving other types of memory, also require neural overcompensation in at-risk individuals, even when they are young.

"However, even if our results show a lack of effects of sports on memory in at-risk individuals, they should not undermine the beneficial impacts of physical activity on overall synaptic plasticity. For any individual, whether at risk or not of developing Alzheimer's disease, physical exercise remains beneficial for neural and cognitive health throughout life," conclude the authors.