A large German study that has just been presented at the Copenhagen ECNP Congress shows that in young adults, the fitter you are, the better your brain works and is organized, too. This could possibly mean that helping people with impaired thinking and memory to become fit could help boost their cognitive functioning. It could also help enhance brain structure.
Earlier studies showed a distinct link between health and brain functioning at all ages, and at all levels of mental functioning. However, the presence of numerous confounding factors which might by themselves account for or contribute to such a link made it hard to tell what actually caused the improvement. For instance, body weight, education, age and blood glucose levels all influence both brain function, in addition to physical fitness. Moreover, it is uncommon to look at brain structure in relation to exercise, though one study showed a positive association between fitness, working memory and normal white matter microstructure. A few other studies have showed better cognitive performance and increased gray matter in the hippocampus, or better white matter integrity in the temporal and prefrontal area, after adopting aerobic exercise for 12 months.
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How was the study done?
The current study used a public database from the Human Connectome Project, containing information collected from volunteers who wished to help progress in scientific research. Over 1,200 MRI scans of the brain were retrieved to assess the microscopic structure of the white matter, using a technique called diffusion tensor imaging. Some additional tests were run on the volunteers, who were on average 29 years old, with a mean BMI of 27.
First, they did a two-minute walking test, to assess the distance covered at top speed in two minutes. Next they did a set of tests on cognitive function looking at aspects like memory, judgment, acuity and logic.
What did the study show?
The test performances showed that in this age group, the better the fitness (as shown by increased distance on speed walking), the better the individual did on cognitive testing in almost every area. The least significant effect was in the area called list sorting which tests working memory, and could mean that working memory is the most sensitive to metabolic conditions like high blood glucose or blood pressure, or obesity.
In these individuals, the brain scans showed better structural integrity of the white matter. They used a measure called fractional anisotropy (FA) which was found to be increased over the whole brain in fitter people. The brain’s white matter contains the millions of nerve connections that are responsible for every neutrally-regulated event in the body, and its structure is vital to transmit nerve impulses rapidly and smoothly.
They also found that episodic memory and white matter microstructure associations were responsible for the positive effect of increased fitness upon white matter microstructure. This may mean that exercise can enhance episodic memory by means of better white matter integrity.
These results remained unchanged after accounting for all confounding factors.
What do we learn?
The study thus emphasizes the vital link between fitness and mental function, even in a young healthy population. Researcher Jonathan Repple says, “We knew how this might be important in an elderly population which does not necessarily have good health, but to see this happening in 30 year olds is surprising. This leads us to believe that a basic level of fitness seems to be a preventable risk factor for brain health.”
The study also throws up a bigger query: if fitness is associated with better brain health, should fitness be encouraged in order to promote improved brain health? This cause-effect relationship must be explored, and this is the next step. Repple says, “There are some trials which point in that direction, but if we can prove this using such a large database, this would be very significant.”
This trial was remarkable for the large sample size, where most MRI-based studies deal with at most a few dozens of scans. Here, says Repple, “the existence of this large MRI database allowed us to eliminate possibly misleading factors, and strengthened the analysis considerably.”
The study was published in the journal Scientific Reports on September 9, 2019.
White matter microstructure mediates the association between physical fitness and cognition in healthy, young adults. Nils Opel, Stella Martin, Susanne Meinert, Ronny Redlich, Verena Enneking, Maike Richter, Janik Goltermann, Andreas Johnen, Udo Dannlowski & Jonathan Repple. Scientific Reports 9; 12885 (2019). https://www.nature.com/articles/s41598-019-49301-y