For middle aged people, too much time on the couch watching television instead of exercising could shrink their brains, according to a new study.
Writing in the journal Neurology, researchers from the Boston University School of Medicine found that less fit middle-aged adults saw loss of brain volume after 20 years.
?We found a direct correlation in our study between poor fitness and brain volume decades later, which indicates accelerated brain aging,? said study author Nicole Spartano of Boston University School of Medicine.
For their study, researchers looked at over 1,500 people from the Framingham Heart Study, or FHS, a project of the National Heart, Lung, and Blood Institute and Boston University. The subjects were age 40 on average and did not have dementia or heart disease. They were given a treadmill test.
Two decades later, researchers looked at the same group, minus any who had developed heart disease or high blood pressure. This group consisted of just over 1,000 people.
Each group was then given MRI brain scans.
FHS participants? health has been monitored since 1975, using information gleaned from ?FHS exams, outside clinical records, interviews with family members, and the examination of participants suspected of having a neurological problem by neurologists and neuropsychologists.?
During the treadmill tests, the participants had an estimated ?exercise capacity? (of 39 mL/kg/min), also known as VO2 or ?the maximum amount of oxygen the body is capable of using in one minute.?
Exercise capacity was estimated by monitoring the amount of time a subject could exercise before his or her heart rate passed a threshold.
The researchers found that for every eight units lower the subjects performed on the treadmill test, ?their brain volume two decades later, was smaller, equivalent to two years of accelerated brain aging.?
When the researchers exclude patients with heart disease or those who take beta blockers for high blood pressure, ?every eight units of lower physical performance was associated with reductions of brain volume equal to one year of accelerated brain aging.?
Those subjects who saw their blood pressure and heart rate surge the most during the treadmill test were ?more likely to have smaller brain volumes two decades later,? researchers wrote.
Spartano warns that the study is ?observational? and ?does not prove that poor physical fitness causes a loss of brain volume,? but that there is an association between the two.
?While not yet studied on a large scale, these results suggest that fitness in middle age may be particularly important for the many millions of people around the world who already have evidence of heart disease,? she said.