Exercise Tied to Slower Cognitive Decline in Those at Risk for AD

Megan Brooks

August 19, 2021

Moderate to high levels of regular physical activity may help slow cognitive decline in older adults with higher and, to a less extent, lower total tau concentrations, new research suggests.

Lead author Pankaja Desai, PhD, assistant professor, Rush Institute for Healthy Aging, Chicago, Illinois, told Medscape Medical News that the examination of total tau in blood is a fairly new area of interest in the field.

"Limited research has been done to understand the relationships between total tau, physical activity, and cognitive function," Desai said.

"Our findings may support using blood biomarkers to further develop risk profiles and may provide the chance for intervening early," she added.

The findings were published online August 11 in JAMA Network Open.

Sedentary Lifestyle Hard on the Brain

The study included 1159 participants (mean age, 77.4 years; 63% women; 60% Black) in the longitudinal, population-based Chicago Health and Aging Project (CHAP).

As part of the ongoing study, relevant data ― including self-reported physical activity levels, total serum tau concentrations, and results on standard cognitive function tests ― are collected every 3 years.

Medium activity was defined as participating in less than 150 minutes of physical activity per week. High activity was defined as engaging in 150 minutes or more of physical activity per week.

Among all participants, 400 (35%) reported participating in a medium level of physical activity, and 402 (35%) participated in a high level of activity. In addition, 357 (31%) reported engaging in little physical activity.

Among individuals with low total tau concentrations (≤0.40 pg/mL), baseline global cognitive function scores were 47% higher among those with medium physical activity and 41% higher for those with high physical activity compared with peers with little physical activity.

For participants with high total tau concentrations (>0.40 pg/mL), those with medium and high levels of physical activity had 8% better cognitive function at baseline in comparison with participants with little physical activity.

Also among individuals with high total tau, medium physical activity was associated with a 58% slower rate of cognitive decline over time in comparison with little physical activity, and high physical activity was associated with a 41% slower rate of cognitive decline.

In participants with low total tau, medium physical activity was associated with a 2% slower rate of cognitive decline, and high physical activity was associated with a 27% slower rate of cognitive decline compared with little physical activity.

Strengths and Weaknesses

Participants with little physical activity and high total tau concentrations experienced a "substantial decline across all cognitive outcomes and, inversely, participants with high physical activity and low total tau concentrations tended to sustain high scores over time," the investigators report.

"These results suggest that physical activity may have a positive association with cognitive function and that sedentary behavior may have a negative association with cognitive function," they write.

Desai said it is not surprising that physical activity had less of an impact on cognition in those with lower levels of total tau.

"Individuals with high total tau concentrations may have increased rates of cognitive decline compared to those with low total tau concentrations," she noted. "Therefore, the impact of physical activity may be less pronounced on cognitive decline among individuals with low total tau concentrations as opposed to those with high total tau concentrations."

Study strengths cited by the researchers include the large, population-based, biracial sample; use of serum biomarkers; and having at least two measurement points of cognitive function.

They caution, though, that the direction of causation in the association between physical activity and pathology of Alzheimer's disease remains unclear and that cutoffs for biomarker measurements are not well established.

The researchers note that use of self-reports to measure physical activity was another limitation.

"Intriguing" Question, Replication Needed

Commenting on the findings for Medscape Medical News, Claire Sexton, DPhil, director of scientific programs and outreach for the Alzheimer's Association, said the study addresses the "intriguing" question of whether physical activity is associated with reduced cognitive decline among individuals with high tau levels.

"The results of this study are interesting too and, if replicated, could be noteworthy," said Sexton, who was not involved with the research.

"As a single study, though, it is too early for nuanced clinical implications beyond the general recommendation to patients that exercise is good for the brain. Evidence is strong that regular physical activity reduces cardiovascular risk factors that may contribute to dementia risk," Sexton said.

She added that it is "never too early or too late to adopt healthy lifestyle activities," such as exercise and a heart-healthy diet.

Sexton also applauded the fact that 60% of the study participants were Black.

"Being that African Americans are disproportionately affected by Alzheimer's disease and cardiovascular disease, it's incredibly important to continue research in this population," she said.

The study was supported by grants from the National Institutes of Health. Desai and Sexton have disclosed no relevant financial relationships.

JAMA Netw Open. Published online August 11, 2021. Full article

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