Dementia: Adding 7-9 minutes of exercise per day may boost cognition

  • Researchers investigated the effects of different types of movement behavior on midlife cognition.
  • They found that trading as little as 7-9 minutes of sedentary behavior for moderate or vigorous physical activity could significantly improve cognition.
  • The findings suggest that higher levels of moderate or vigorous physical activity could improve cognition.

Physical activity is linked to the building of cognitive reserve, which delays the onset of cognitive decline later in life.

A systematic review found that higher levels of physical activity and less sedentary behavior is linked to better cognition in older adults. Few studies, however, have explored the link between physical activity and cognition among adults in midlife.

Few studies have also assessed the effects of sleep time on cognition, despite it typically being the largest component of the day, and a major confounder of cognitive test performance.

Further research that assesses the effects of movement behavior and sleep on midlife cognition could help improve prevention strategies for cognitive decline at a later age.

Recently, researchers assessed the link between cognitive test scores and 24-hour movement behaviors from 4,481 U.K.-based participants.

“We identified that individuals spending even small amounts of more time in more vigorous activities—as little as [around] 6-9 minutes—compared to sitting, sleeping or gentle activities had higher cognition scores,” John Mitchell, MRC doctoral student, UCL Institute of Epidemiology and Health Care, one of the study’s authors, told Medical News Today.

The study was published in the Journal of Epidemiology and Community Health.

Moderate physical activity improves cognition

The researchers analyzed data from the 1970 British Cohort Study, a prospective birth cohort study of U.K.-born adults. Altogether, they assessed data from 4,481 participants at an average of 47 years old.

For the study, participants undertook cognitive tests of verbal memory and verbal fluency and wore an accelerometer device for up to seven days to measure movement behaviors, including:

  • Sedentary behavior, such as non-sleep time spent sitting or lying down
  • Light, moderate, and vigorous physical activity
  • Sleep time

The researchers also considered demographic data alongside measures of education attainment, disability, and health and lifestyle factors, including alcohol consumption and cigarette smoking.

They found that moderate and vigorous physical activity, or MVPA, was positively related to cognition. While the relationship remained after adjusting for sociodemographic factors, it reduced after accounting for health and lifestyle factors.

Even after adjusting for sociodemographic, health, and lifestyle factors, sedentary behavior remained positively liked to cognition.

They also found that more time spent in light-intensity physical activity or sleep was inversely linked to cognition. However, only sleep remained inversely linked to cognition after adjusting for all factors.

How much time to see benefit

Next, the researchers investigated the cognitive effects of adjusting time allocations between movement activities. To do so, they built a predictive model based on the average time participants spent in each movement behavior:

  • 51 minutes in MVPA
  • 5 hours 42 mins in light physical activity
  • 9 hours 16 minutes in sedentary behavior
  • 8 hours 11 minutes sleeping

The researchers then predicted the cognitive effects of reallocating time from one movement activity to another.

In doing so, they found that cognition scores significantly increased after replacing 9 minutes of sedentary behavior with MVPA.

They also found that replacing 37 minutes of light physical activity or 56 minutes of sleep with sedentary behavior had a positive effect on cognition in their predictive model.

Reduction of MVPA in favor of other behaviors had a negative effect on cognition. These effects were seen after 8 minutes of MVPA was replaced by sedentary behavior, 6 minutes by light physical activity, and 7 minutes by sleep.

How movement is linked to cognition 

To understand how exercise might be linked to better cognition, MNT spoke with Dr. Victoria Williams, assistant professor in the Geriatrics Faculty of the University of Wisconsin School of Medicine and Public Health, who was not involved in the study.

“We know that regular exercise increases our cardiorespiratory fitness (CRF), which is the efficiency of the circulatory and respiratory systems to supply oxygenated blood to our vital organs,” she said.

“CRF is most readily improved through periods of sustained moderate to vigorous physical activity, which aligns with results from this study suggesting that even 6–8 minutes of MVPA replaced with less active behaviors proves deleterious for cognitive functioning. Because of the high metabolic demands of the brain, it is highly susceptible to changes in blood supply,” she elaborated.

MNT also spoke with Dr. Achillefs Ntranos, board certified neurologist, who was also not involved in the study.

“Exercise has been shown to increase the production of growth factors, such as brain-derived neurotrophic factor (BDNF), which promote the growth and survival of neurons in the brain. This may lead to improved brain plasticity and cognitive function,” he said about the possible mechanisms behind this finding.

“Another potential mechanism [behind how exercise imrpoves cognition] is that moderate to vigorous physical activity leads to the formation of new neurons in the hippocampus, a region of the brain involved in memory and learning. This is known as neurogenesis.”
— Dr. Achillefs Ntranos

The researchers wrote that the seemingly positive effects of sedentary behavior may be reflective of how people spend sedentary time.

For example, cognitively stimulating reading or working may affect cognition differently than less-stimulating tasks such as watching television.

Not all activities have the same effect

MNT asked Dr. Clay Johnston, a board certified neurologist, co-founder of Harbor Health, and the inaugural dean of Dell Medical School, The University of Texas at Austin, about the study’s limitations.

“The study can’t tell us whether exercise improves cognition [or] whether those with higher cognition exercise more, which seems just as likely. Though the authors try to adjust for factors that might be associated with higher cognition and exercising more, those sorts of adjustments are never perfect,” he said.

Elexander Atkinson, a family medicine provider at Novant Health in Cornelius, North Carolina, who was also not involved in the study, pointed out to MNT a few biases.

“One was the selection: mostly white males and females, making it difficult to apply broadly to different races and ethnicities. Additionally, it was performed in the U.K., so it may not be as applicable in other countries,” he said.

“They did not measure sleep quality, which certainly could play a large role in [the] outcomes they are measuring; they do mention this. Overall, the study does a good job of showing that moderate exercise is an important component of cognitive function,” he added.

Ryan Glatt, a certified personal trainer and health and wellness coach, and director of the FitBrain Program at the Pacific Neuroscience Institute in Santa Monica, California, who was not involved in the study, told MNT that there were some challenges in tracking participants’ behavior.

“When wearing an accelerometer, we do not know what sorts of activities individuals are doing. Even when an individual is sedentary, they can be engaging in cognitively stimulating tasks, which can be beneficial for cognition,” said Glatt.

“In addition, not all physical activities, nor varied intensities, may have the same effects on the brain, and while all activities can be beneficial, no activity has been found to be superior to another,” he added.

Increasing physical activity will help

When asked what the main takeaway from this research might be, Dr. Russell Swerdlow, professor of neurology & molecular and integrative physiology at the University of Kansas KU Medical Center, who was not involved in the study, told MNT:

“Many want to know if it is within their hands to control their cognitive performance level or cognitive destiny. This study is consistent with this possibility but does not prove this possibility.”

“Those who do not want to wait for a more definitive answer may, in the meantime, decide to [adopt] a greater level of physical activity, as that adjustment is unlikely to have a negative impact,” he added.

Dr. Alex Dimitriu, double board certified in psychiatry and sleep medicine and founder of Menlo Park Psychiatry & Sleep Medicine, agreed that adopting greater levels of physical activity is a main takeaway.

“Movement is key! And also active mental engagement—reading over passive television—or videos online. The human body and brain really do adhere to a ‘use it or lose it’ policy. Physical activity has numerous health benefits, many of which are cardiovascular, which in turn have direct benefits to the brain, and cognition and memory.”
— Dr. Alex Dimitriu

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