The results of this study can be added to the many reasons to keep up with a decent level of exercise. A sedentary lifestyle has costs, most of which manifest as a greater risk of age-related disease in later later:
Poor physical fitness in middle age may be linked to a smaller brain size 20 years later. "We found a direct correlation in our study between poor fitness and brain volume decades later, which indicates accelerated brain aging." For the study, 1,583 people enrolled in the Framingham Heart Study, with an average age of 40 and without dementia or heart disease, took a treadmill test. They took another one two decades later, along with MRI brain scans. The researchers also analyzed the results when they excluded participants who developed heart disease or started taking beta blockers to control blood pressure or heart problems; this group had 1,094 people.
Exercise capacity was estimated using the length of time participants were able to exercise on the treadmill before their heart rate reached a certain level. For every eight units lower a person performed on the treadmill test, their brain volume two decades later was smaller, equivalent to two years of accelerated brain aging. When the people with heart disease or those taking beta blockers were excluded, every eight units of lower physical performance was associated with reductions of brain volume equal to one year of accelerated brain aging. The study also showed that people whose blood pressure and heart rate went up at a higher rate during exercise also were more likely to have smaller brain volumes two decades later. People with poor physical fitness often have higher blood pressure and heart rate responses to low levels of exercise compared to people with better fitness.