What brain scans reveal about people who move more

New research indicates that physical movement may help preserve the ability to recall numbers over short periods by maintaining the structural integrity of the brain. These findings highlight potential biological pathways connecting an active lifestyle to cognitive health in later life. The analysis was published in the European Journal of Neuroscience.

As the global population ages, the prevalence of cognitive impairment and dementia has emerged as a primary public health concern. Memory decline compromises daily independence and social engagement. Medical experts have identified physical inactivity as a modifiable risk factor for this deterioration.

Prior investigations have consistently linked exercise to better cognitive performance. Researchers have found that older adults who maintain active lifestyles often exhibit preserved memory and executive function. However, the biological mechanisms driving this protective effect remain only partially understood.

The brain undergoes physical changes as it ages. These changes often include a reduction in volume and the accumulation of damage. Neuroscientists categorize brain tissue into gray matter and white matter.

Gray matter consists largely of neuronal cell bodies and is essential for processing information. White matter comprises the nerve fibers that transmit signals between different brain regions. The integrity of these tissues is essential for optimal cognitive function.

Another marker of brain health is the presence of white matter hyperintensities. These are small lesions that appear as bright spots on magnetic resonance imaging scans. They frequently indicate disease in the small blood vessels of the brain and are associated with cognitive decline.

Previous studies attempting to link activity with brain structure often relied on self-reported data. Surveys asking participants to recall their exercise habits are prone to inaccuracies and bias. People may not remember their activity levels correctly or may overestimate their exertion.

To address these limitations, a team of researchers conducted a large-scale analysis using objective data. The study was led by Xiaomin Wu and Wenzhe Yang from the Department of Epidemiology and Biostatistics at Tianjin Medical University in China. They utilized data from the UK Biobank, a massive biomedical database containing genetic and health information.

The researchers aimed to determine if objectively measured physical activity was associated with specific memory functions. They also sought to understand if structural markers in the brain could explain this relationship statistically. They focused on a sample of middle-aged and older adults.

The final analysis included 19,721 participants. The subjects ranged in age from 45 to 82 years. The study population was predominantly white and had a relatively high level of education.

Physical activity was measured using wrist-worn accelerometers. Participants wore these devices continuously for seven days. This method captured all movement intensity, frequency, and duration without relying on human memory.

The researchers assessed memory function using three distinct computerized tests. The first was a numeric memory test. Participants had to memorize a string of digits and enter them after they disappeared from the screen.

The second assessment was a visual memory test involving pairs of cards. Participants viewed the cards briefly and then had to match pairs from memory. The third was a prospective memory test, which required participants to remember to perform a specific action later in the assessment.

A subset of 14,718 participants also underwent magnetic resonance imaging scans. These scans allowed the researchers to measure total brain volume and the volumes of specific tissues. They specifically examined gray matter, white matter, and the hippocampus.

The hippocampus is a seahorse-shaped structure deep in the brain known to be vital for learning and memory. The researchers also quantified the volume of white matter hyperintensities. They then used statistical models to look for associations between activity, brain structure, and memory.

The study found a clear positive association between physical activity and performance on the numeric memory test. Individuals who moved more tended to recall longer strings of digits. This association held true even after adjusting for factors like age, education, and smoking status.

The results for the other memory tests were less consistent. Physical activity was not strongly linked to prospective memory. The link to visual memory was weak and disappeared in some sensitivity analyses.

When examining brain structure, the researchers observed that higher levels of physical activity correlated with larger brain volumes. Active participants had greater total brain volume. They also possessed higher volumes of both gray and white matter.

The scans also revealed that increased physical activity was associated with a larger hippocampus. This was observed in both the left and right sides of this brain region. Perhaps most notably, higher activity levels were linked to a lower volume of white matter hyperintensities.

The researchers then performed a pathway analysis to understand the mechanism. This statistical method estimates how much of the link between two variables is explained by a third variable. They tested whether the brain structures mediated the relationship between activity and numeric memory.

The analysis showed that brain structural markers explained a substantial portion of the memory benefits. Total brain volume, white matter volume, and gray matter volume all acted as mediators. White matter hyperintensities played a particularly strong role.

Specifically, the reduction in white matter hyperintensities accounted for nearly 30 percent of the total effect of activity on memory. This suggests that physical activity may protect memory partly by maintaining blood vessel health in the brain. Preventing small vessel damage appears to be a key pathway.

The findings indicate that physical activity helps maintain the overall “hardware” of the brain. By preserving the volume of processing tissue and connection fibers, movement supports the neural networks required for short-term memory. The preservation of white matter integrity seems particularly relevant.

The researchers encountered an unexpected result regarding the hippocampus. Although physical activity was linked to a larger hippocampus, this volume increase did not explain the improvement in numeric memory. The pathway analysis did not find a significant mediating effect for this specific structure.

The authors suggest this may be due to the nature of the specific memory task. Recalling a string of numbers is a short-term working memory task. This type of cognitive effort relies heavily on frontoparietal networks rather than the hippocampus.

The hippocampus is more closely associated with episodic memory, or the recollection of specific events and experiences. The numeric test used in the UK Biobank may simply tap into different neural circuits. Consequently, the structural benefits to the hippocampus might benefit other types of memory not fully captured by this specific test.

The study provides evidence that the benefits of exercise are detectable in the physical structure of the brain. It supports the idea that lifestyle choices can buffer against age-related degeneration. The protective effects were observed in a non-demented population, suggesting benefits for generally healthy adults.

There are several important caveats to consider regarding this research. The study was cross-sectional in design. This means data on activity, brain structure, and memory were collected at roughly the same time.

Because of this design, the researchers cannot definitively prove causality. It is possible that people with healthier brains find it easier to be physically active. Longitudinal studies tracking changes over time are necessary to confirm the direction of the effect.

Another limitation is the composition of the study group. The UK Biobank participants tend to be healthier and wealthier than the general population. This “healthy volunteer” bias might limit how well the findings apply to broader, more diverse groups.

The measurement of physical activity, while objective, was limited to a single week. This snapshot might not perfectly reflect a person’s long-term lifestyle habits. However, it is generally considered more reliable than retrospective questionnaires.

Future research should explore these relationships in more diverse populations. Studies including participants with varying levels of cardiovascular health would be informative. Additionally, using a wider array of memory tests could help map specific brain changes to specific cognitive domains.

Despite these limitations, the study reinforces the importance of moving for brain health. It suggests that physical activity does not just improve mood or heart health. It appears to physically preserve the brain tissue required for cognitive function.

The preservation of white matter and the reduction of vascular damage markers stand out as key findings. These structural elements provide the connectivity and health necessary for the brain to operate efficiently. Simple daily movement may serve as a defense against the structural atrophy that often accompanies aging.

The study, “Association Between Physical Activity and Memory Function: The Role of Brain Structural Markers in a Cross-Sectional Study,” was authored by Xiaomin Wu, Wenzhe Yang, Yu Li, Luhan Zhang, Chenyu Li, Weili Xu, and Fei Ma.