Physical Activity May Offset Tau-Related Cognitive Decline

Source: Gerd Altmann/Pixabay

Researchers from the Rush Institute for Healthy Aging at the Rush University Medical Center in Chicago recently completed an original investigation into the long-term association between total tau concentrations, various weekly physical activity levels, and cognitive decline. Their findings (Desai et al., 2021) were published on August 11 in the open-access journal JAMA Open Network.

The population sample for this study included 1,159 older adults with an average age of 77.4. Research data for this longitudinal study was collected between 1993 and 2012.

The main objective of this first-of-its-kind study was to investigate how different weekly levels of physical activity (or inactivity) are associated with the speed of cognitive decline in older adults with varying levels of tau.

As first author Pankaja Desai and coauthors explain: "To our knowledge, ours is the first study to longitudinally evaluate physical activity in the association between total tau in serum and cognitive function."

Although higher tau levels are associated with amnestic mild cognitive impairment (MCI) and tau is abnormally phosphorylated in the brains of patients with Alzheimer's disease (AD), more research is needed to understand the specific role that tau plays in the progression of neurodegenerative diseases and cognitive decline.

That said, measuring total tau concentrations presents a unique opportunity to use biomarkers to assess the neuroprotective efficacy of lifestyle interventions such as daily physical activity.

≥150 Minutes of Exercise per Week Differentiates "Medium Activity" from "High Activity"

At baseline, study participants in the "little activity" group—who self-reported that they hadn't participated in any physical activity (e.g., walking for exercise, jogging or running, bicycle riding, swimming or water aerobics, dancing, gardening or yard work, etc.) in the past 14 days—tended to have lower cognitive function scores than those in the "medium" and "high" physical activity groups.

Participants who met the recommended physical activity guidelines and self-reported doing more than 150 minutes of exercise per week were put in the "high activity" group; those who fell below this threshold but did some physical activity each week were classified as "medium activity."

Notably, during this longitudinal study, the researchers found that "participants with medium physical activity and high physical activity had slower cognitive decline compared with participants with little physical activity within both total tau concentration groups."

Medium and High Levels of Physical Activity Can Slow Cognitive Decline

In comparison to the little physical activity group, among participants with high total tau concentrations, "medium physical activity was associated with a 58% slower rate of cognitive decline, and high physical activity was associated with a 41% slower rate of cognitive decline."

However, for study participants with low total tau concentrations at baseline, "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."

Based on these findings, the authors sum up: "This study suggests that, among participants with both high and low total tau concentrations, physical activity was associated with slower cognitive decline."

One significant limitation of this research is that physical activity data was self-reported, which often skews results. Also, data limitations prevented researchers from specifically categorizing the intensity and duration of participants' daily workouts each week.

For example, this study doesn't differentiate between moderate-to-vigorous physical activity (MVPA), high-intensity interval training (HIIT), or weight-resistance training, which may each have different dose responses. As Herold et al. (2019) proclaim: "Dose-Response Matters!" in exercise-cognition research.

More research is needed to pinpoint how a combination of strength training, MVPA, and HIIT workouts should be mixed and matched each week to create the best dose-response and optimize physical activity's ability to offset cognitive decline. "Future work should examine the association of total tau concentrations with other health behaviors and physical activity types," Desai et al. conclude.