Researchers examined data on 1,159 adults with a mean age of 77.4 years who reported their physical activity levels and had clinical evaluations including at least one blood test for tau concentrations as well as a mean of 3 cognitive assessments between 1994 and 2012. At baseline, 337 participants got little to no physical activity; 400 people reported "medium" physical activity levels of less than 150 minutes per week; and 402 reported "high" physical activity levels of at least 150 minutes per week.
Among participants with high total tau concentrations (above 0.40 pg/mL), medium physical activity was associated with a 58% lower rate of cognitive decline during the study period and high physical activity was associated with a 41% slower rate of cognitive decline, compared with little physical activity.
For participants with low total tau concentrations (up to 0.40 pg/mL), medium physical activity was associated with a 2% slower rate of cognitive decline and high physical activity was associated a 27% lower rate of cognitive decline compared with little physical activity.
"Although the finding indicated in the question is not surprising, it has important implications for public health, suggesting that despite being at higher risk, physical activity may slow rate of cognitive decline," said lead study author Pankaja Desai, an assistant professor at the Rush Institute for Healthy Aging at Rush University Medical Center in Chicago.
The study results not only suggest that maintaining physical activity could slow cognitive decline, they also suggest that blood biomarker concentrations might help clinicians identify high-risk patients and target them for earlier intervention, Desai said by email.
Physical activity was assessed based on questions from the 1985 U.S. Health Interview Survey, which asks respondents to report the frequency and duration of participation in a wide variety of activities such as walking, gardening, bowling, or physically active hobbies.
Cognitive function was assessed using the East Boston Tests of Immediate Memory and Delayed Recall, the Mini-Mental State Examination, and a modified oral version of the Symbol Digit Modalities Test.
One limitation of the study is that self-reported physical activity can be subject to social desirability bias, the researchers note in JAMA Network Open.
Another limitation is that a far larger proportion of participants reported high activity levels than is typical in the general population, which might limit the generalizability of the study results.
Plasma total tau is thought to be a marker of neurodegeneration that is independent of elevated brain amyloid - thus, not specific for Alzheimer's disease, said Michelle Mielke, a professor of epidemiology and neurology at the Mayo Clinic College of Medicine in Rochester, Minnesota, who wasn't involved in the study.
"High levels of total tau may be indicative of more neurodegeneration so the results would suggest that for individuals who already have notable neurodegeneration, physical activity can help to mitigate cognitive decline," Mielke said by email. "For those individuals who have low neurodegeneration but high physical activity, cognitive decline is also mitigated but not as much."
SOURCE: https://bit.ly/3sNo0JB JAMA Network Open, online August 11, 2021.
By Lisa Rapaport
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