Exercise Science: Effects on Cognitive Decline Begin Earlier Than Thought

As brilliant as humans are, we’re working with limited cognitive resources that decline over time. There’s a whole field of research desperately searching for ways to fight the ravages of aging on the brain, and neuroscientists at Columbia University think they have a solution. The good news is it requires nothing more than some motivation — and maybe a heart rate monitor.

Columbia neuropsychologist Yaakov Stern, Ph.D., the lead author of a paper published Wednesday in the journal Neurology, found that a regular exercise program seemed to improve “executive function” in 132 individuals who ranged in age from their early 20s to late 60s. Executive function, says Stern, is an important collection of cognitive abilities that help us plan ahead, reason things out, or solve complex problems (it’s recently been linked to big, smart dogs). Unfortunately, executive function eventually hits a peak at a certain age (that age depends on the person) and then declines as aging takes its toll on cognition.

In his trial, Stern found that exercise seemed to slow that natural decline in executive function, which is good news for anyone looking for a simple way to stay sharp as they age. Somewhat surprisingly, he also found that aerobic exercise could improve executive function in participants as young as 20, which may protect against declines in executive function later in life.

“We hoped that aerobic exercise would improve cognitive function in younger people, this had not been tested previously in a relatively large, controlled trial,” Stern tells Inverse. “I think that the improvements that we saw in executive function associated with aerobic exercise are sizable enough to be meaningful, even for someone in their 20s.”

In his study, Stern had his subjects of all ages perform four workouts per week for six months. They either did an aerobic workout in specific heart rate zones — roughly 75 percent of their maximum heart rate — or did stretching and core exercises. The team then tested the volunteers’ executive function in a series of memory or speed association tasks twice: once at the halfway point, and once at the end of the six month trial. There, he reported that there were statistically significant improvements in the scores for people of every age who were in in the aerobic exercise group — even the 20-year-olds.

But when Stern reviewed the results of his executive function tests he noted that the older someone was, the more drastic their score improvements from baseline were to begin with, suggesting that the bigger takeaway from his study isn’t that exercise improves cognition in the short term, it’s that it can slow declines in cognition that snowball as we get older.

“What we saw is that the impact of exercise on executive function increased with age, such that, for example, someone age 40 improve more than someone age 30,” adds Stern. “Since executive function decreases with age, this makes us think that exercising reverses the decline in cognition as opposed to enhancing cognition.”

Stern explains that exercise may be beneficial to brain function because it can “increase vascularization in the brain” — helping make blood flow more consistent. He also suspects exercise promotes plasticity, which keeps brain cells versatile and able to form new connections. As part of this study, Stern actually noted that participants in the aerobic exercise group increased the “cortical thickness” of their brains — the outer layer of brain matter.

That increase in cortical thickness is important because cortical thinning is actually associated with disease of aging that plague the aging brain, like dementia. Aerobic exercise improved cortical thickness in people as young as 20, who probably aren’t experiencing significant cognitive declines yet. Stern adds that an implication of his data is that creating a regular exercise practice early in life could help the brain start to build up these crucial defenses.

In the paper, he writes that the team’s findings “extends the demonstrated benefits of aerobic exercise to individuals as young as 20,” and suggest that exercise could be a potential intervention for brain health in adults of all ages.

Twenty-somethings may not have to worry about cognitive declines just yet, but it seems like a few workouts a week may make them better prepared to fight off the effects of aging on the brain as they grow near.

Abstract:

Objective: To determine efficacy of aerobic exercise for cognitive function in younger healthy adults.

Methods: In a randomized, parallel-group, observer-masked, community-based clinical trial, 132 cognitively normal individuals aged 20–67 with below median aerobic capacity were randomly assigned to one of two 6-month, 4-times-weekly conditions: aerobic exercise and stretching/toning. Efficacy measures included aerobic capacity; cognitive function in several domains (executive function, episodic memory, processing speed, language, and attention), everyday function, body mass index (BMI), and cortical thickness.

Results: Aerobic capacity increased significantly (β = 2.718; p = 0.003), and BMI decreased significantly (β = −0.596; p = 0.013) in the aerobic exercise but not in the stretching/toning condition. Executive function improved significantly in the aerobic exercise condition; this effect was moderated by age (β = 0.018 SD/y; p = 0.028). At age 40, the executive function measure increased by 0.228 SD (95% confidence interval [CI] 0.007–0.448), and by 0.596 SD (95% CI 0.219–0.973) at age 60. Cortical thickness increased significantly in the aerobic exercise group in a left frontal region and did not interact with age. Controlling for age and baseline performance, individuals with at least one APOE ε4 allele showed less improvement in executive function with aerobic exercise (β = 0.5129, 95% CI 0.0381–0.988; p = 0.0346).

Conclusions: This randomized clinical trial demonstrates the efficacy of aerobic exercise for cognition in adults age 20–67. The effect of aerobic exercise on executive function was more pronounced as age increased, suggesting that it may mitigate age-related declines. Increased cortical thickness suggests that aerobic exercise contributes to brain health in individuals as young as age 20.