Researchers at Boston University School of Medicine examined the link between brain tissue volume in elderly people and their activity levels when they were twenty years younger. The result showed that the participants who were less active physically when they were younger were more likely to have smaller brain tissue as they grew older.
Younger participants were tested on a slow-speed treadmill in order to measure their diastolic blood pressure and heart rate to assess fitness levels. 20 years later they went back to have their brain tissue volume measured with MRI’s and cognitive testing.
People who were not fit have higher spikes in diastolic blood pressure and heart rate throughout their day. Even though the test concluded that more physical exercise equals less brain shrinkage, it did not figure out why this is. There is a possibility that the increased oxygen delivery and better artery health that come with fitness have some way to protect the brain as well.