The longer you can run when you're young, the faster your mind is likely to be operating in middle age, a new study suggests.
Researchers found that better cardiac fitness in young adults translated to better brain fitness 25 years later, adding to a growing body of evidence that links heart health with mental functioning.
"Our study links fitness, which can be influenced by vigorous activity, but also by general engagement with life and the community or 'being part of things,' with poorer thinking skills at age ages 43 to 55 years," author David R. Jacobs told Reuters Health by email.
Jacobs worked on the new study at the University of Minnesota in Minneapolis.
He and his co-authors analysed data on 2,700 men and women over a 25-year period. The participants were recruited in 1985, when they were all between 18 and 30 years old.
In 1985, all participants did a short treadmill test to assess their fitness. The researchers recorded how long each person could maintain running at their top speed.
There were seven follow-up checks over the next 25 years.
At the last one, in 2010, researchers tested the participants' mental functioning with three tests of visual memory, reaction speed and the kind of mental control needed to answer a trick question, such as identifying the colour of the word yellow written in green ink (correct answer: "green").
In general, people who were more fit at the beginning of the study were more likely to have higher education, to smoke less, to be active more often and to have healthy blood pressure and lower cholesterol than people who were less fit.
For the memory test, researchers showed each person a list of 15 words, then 10 minutes later asked them to recall those words.
When they looked at participants' fitness as young adults, they found that for every extra minute an individual could keep sprinting on the treadmill back then, the person remembered .12 more words correctly on the memory test 25 years later.
People who were fitter in youth also performed noticeably better on the reaction speed test and the trick question test, according to the results published in the journal Neurology.
Another recent analysis of the same data linked lower blood pressure and blood sugar in the teen years and twenties with quicker memory and learning skills in middle age (see Reuters Health story of April 1, 2014, here: reut.rs/1or6jez).
The two papers taken together indicate that aspects of behaviour and fitness at average age 25 predict thinking skills at average age 50, Jacobs said.
The mounting evidence suggests that this heart-brain connection begins working early in life, he said.
It is possible that exercising more at an early age simply lowers blood pressure, which then lowers the risk for cognitive decline and dementia, but the researchers took differences in blood pressure into account, Jacobs said, and the results held.
"My interpretation is that something about being more fit, or just doing better on the specific treadmill test that we included, has a connection to better thinking skills," he said.
"We know lifestyle is absolutely fundamental to this whole picture," said Dr. Jennifer G. Robinson, director of the Prevention Intervention Center at the University of Iowa in Iowa City, who was not involved in the new study.
More and more research is identifying subtle changes in heart health early on that predict brain health later, Robinson told Reuters Health.
We can't say yet that physical activity will improve brain function, but it is a good bet that better physical fitness is a positive thing generally, Jacobs said.
"We find many connections between life and biology in youth that predict who has a better or worse profile in late middle age," he said. "Health starts in childhood, or even before birth."