Story highlights Poor physical fitness in middle age might be tied to a smaller brain, researchers found

Health choices made in middle age have consequences many years later, a researcher said

(CNN) Poor physical fitness in middle age might be associated with a smaller brain size later on, according to a study published in an online issue of Neurology.

Brains shrink as people age, and the atrophy is related to cognitive decline and increased risk for dementia, a researcher said, and exercise reduces that deterioration and cognitive decline.

In this study, more than 1,500 people at an average age of 40 and without dementia or heart disease took a treadmill test. Twenty years later, they took another test, along with MRI brain scans. The study found those who didn't perform as well on the treadmill test -- a sign of poor fitness -- had smaller brains 20 years later.

Among those who performed lower, people who hadn't developed heart problems and weren't using medication for blood pressure had the equivalent of one year of accelerated brain aging. Those who had developed heart problems or were using medication had the equivalent of two years of accelerated brain aging.

Their exercise capacity was measured using the length of time participants could exercise on the treadmill before their heart rate reached a certain level. Researchers measured heart rate and blood pressure responses to an early stage on the treadmill test, which provides a good picture for a person's fitness level, according to the study author Nicole Spartano, a postdoctoral fellow at the Boston University School of Medicine.

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