Physical activity reduces cognitive decline but not significantly, researchers find

Key takeaways:

• Researchers found that physical activity was associated with better late-life cognition.
• The association was weak, but it is relevant from a public health perspective, researchers said.

Physical activity was only minimally associated with a reduced risk for cognitive decline or impairment. Even so, the finding was still significant from a population health perspective, according to researchers.

Previous research has similarly suggested that exercise, in combination with cognitive training, could improve brain function and slow cognitive decline.

However, “despite the optimism surrounding physical activity as a means to preserve or improve cognition, many recent high-quality interventional studies urge caution in claims linking cognitive benefits to physical activity,” Paula Iso-Markku, MD, PhD, from the University of Helsinki, Finland, and colleagues wrote in JAMA Network Open.

They added that most of the evidence supporting this relationship comes from observational studies with short follow-ups “and no information on preceding levels of cognition.”

Iso-Markku and colleagues conducted a systematic review and meta-analysis of 104 studies — comprising 341,471 participants — to assess the relationship between physical activity and global and domain-specific cognitive decline.

One of the problems with previous meta-analyses on this topic, the researchers said, was that they only included studies with binary outcomes (ie, “cognitive impairment or cognitive decline or no cognitive impairment or decline”). In their calculations, Iso-Markku and colleagues treated cognition as a continuous variable — a measure they referred to as “follow-up cognition” — to improve statistical power.

The researchers found that physical activity was associated with a decreased incidence of cognitive impairment or decline, after accounting for possible publication bias or other factors that may have swayed the results (pooled RR = 0.97; 95% CI, 0.97-0.99). However, they did not find a significant association between physical activity and cognition in studies with follow-up periods lasting longer than 10 years.

Physical activity also was associated with follow-up global cognition (standardized regression coefficient = 0.03; 95% CI, 0.02-0.03) as well as a change in global cognition (standardized regression coefficient = 0.01; 95% CI, 0.01-0.02).

However, the researchers did not find a clear dose-response relationship between physical activity and cognition, nor was the relationship moderated by factors like study quality, baseline age, follow-up length or adjustment for baseline cognition.

The specific cognitive domains associated with physical activity were:

• verbal fluency (standardized regression coefficient = 0.05; 95% CI, 0.03-0.08); and
• episodic memory (standardized regression coefficient = 0.03; 95% CI, 0.02-0.04)

The researchers explained that although the relationship between physical activity and cognition was weak, it was “significant in a population health perspective for the potential to postpone the multifactorial diseases causing dementia.”

“It should also be noted that very few high-quality studies were included,” they wrote. “Further high-quality cohort studies with follow-ups longer than 10 to 20 years, fine-grained measures of physical activity and cognition at baseline, and high participation and follow-up rates are needed to solidify the evidence base in this area.”