Cognitive benefits from high intensity interval training may last for years

• The brain is a delicate organ that experiences specific changes with age. Older individuals tend to be at a higher risk for developing dementia.
• Researchers are interested in finding what interventions can delay dementia or even improve cognitive function.
• A recent study found that high-intensity interval training, or HIIT, in older adults may help improve hippocampal function and help retain this improvement years after the intervention.

Exercise offers multiple health benefits, and researchers are particularly interested in discovering how it affects the brain function of older adults.

A recent study published in Aging and Disease examined three levels of exercise among healthy older adults and how these interventions affected the functioning of the hippocampus , an area of the brain critical to memory consolidation. Researchers found that participants who engaged in high intensity interval training (HIIT) saw improvement in hippocampal function. They also found that they still saw the improvement up to five years after the start of the intervention.

How does aging affect dementia risk and the hippocampus?

As people age, some changes occur in the brain, and older adults may find certain activities, like paying attention, slightly harder. They may also take longer to learn new skills.

Older adults are also at a higher risk for dementia , making preventive measures and interventions all the more critical in this age demographic. Researchers of the current study note that age can affect the hippocampus. The hippocampus is a critical part of the brain that assists with memory processing, decision making, and conversion of short-term memories into long-term memories. Alzheimer’s disease, a common dementia type, also affects the hippocampus.

Thus, examining how interventions affect this area of the brain could be highly beneficial in addressing cognitive decline in older adults and possibly preventing dementia .

“A key feature of aging dementia is the decline in specific domains of cognitive function, especially those related to spatial learning and memory. The hippocampus is a critical region of the brain that is responsible for the consolidation of spatial information into memories and is particularly susceptible to age, with reports of age-dependent decreased hippocampal volume and connectivity.”

– Study authors

Non-study author Dr. Michele Longo, MD , a neurologist at University Medical Center New Orleans, offered the following insight to Medical News Today :

“Exercised-mediated responses of biomarkers as predictors for improved hippocampal functional outcomes offers a quantifiable metric to provide an effective exercise regimen. The improvement and long-term retention of hippocampal learning ability following HIIT exercise provides a new insight into how the elderly could be insulated from cognitive decline even though their exercise capabilities may decline with advanced age. This approach could greatly enhance the capacity of clinicians to tailor personalized exercise paradigms, including those at risk of cognitive decline.”

Can exercise help improve brain function?

This study was a multidomain, randomized control study. Researchers recruited 194 participants between 65 and 85 years old. They excluded participants who had experienced a stroke, brain trauma , or brain or heart surgery and anyone who was at high risk for experiencing a cardiac event like a heart attack during exercise. Participants did not have diagnosed mental illnesses or cognitive decline at baseline.

Participants were divided into three groups to undergo different levels of exercise intensity:

1. Low-intensity training, which included activities like stretching, range of motion, and balance exercises
2. Medium-intensity training, which was continuous treadmill walking
3. High-intensity training, which included intervals of treadmill work with a more significant increase in heart rate than the medium-intensity training group

The high-intensity training group further combined aerobic and anaerobic exercise.

Participants underwent exercise programs, exercising three days a week for six months under supervision from exercise physiologists. Researchers had participants undergo a number of tests to examine cognitive and hippocampal function, such as the hippocampal-dependent paired associated learning (PAL) test. They also collected monthly blood samples from participants to gain valuable biomarker information.

Researchers conducted cognitive tests monthly during the intervention and followed up with participants every six months afterward for up to five years.

How does exercise intensity affect cognitive improvement?

The study’s results found that the high-intensity interval training group experienced an improvement in hippocampal-dependent spatial learning. The other two groups remained stable rather than showing improvement. This improvement was maintained in the high-intensity interval training group during the five-year follow-up. It appeared to be unrelated to lifestyle and physical activity differences during the follow-up.

Researchers also found that participants who initially performed poorly on PAL assessment initially showed the most improvement if they were part of the high-intensity interval training group. Poor performance participants in the medium-intensity training group also experienced some improvement in these assessments, but less than the high-intensity interval training group. They also found that the high-intensity interval training group had a stable right-hand side hippocampal volume, while the other groups experienced a decrease in this brain area.

With additional brain regions, researchers found the structures to be in better condition in the high and medium-intensity groups than in the low-intensity group. They also observed “improved functional connectivity between multiple neural networks” in the high-intensity interval training group. However, at the 12-month mark, researchers did not observe functional connectivity improvement between network pairs compared to the baseline in any of the groups.

They also observed that changes in certain biomarkers in the high-intensity interval training group correlated with improved associated learning. Researchers did not find that exercise interventions helped improve working memory or emotional recognition.

The results point to the potential brain benefits of exercise, particularly for those engaging in high-intensity interval training.

Non-study author Ryan Glatt, CPT, NBC-HWC , senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in Santa Monica, CA, noted the following clinical implications of the data to Medical News Today :

“The study suggests that high-intensity interval training (HIIT) can significantly improve hippocampal-dependent learning in healthy older adults. While promising, the results should be interpreted cautiously due to potential variability in individual responses to exercise and the study’s specific population. If corroborated by further research, these findings could inform exercise-based interventions for cognitive health in older adults, promoting HIIT as a non-pharmacological strategy to mitigate age-related cognitive decline.”

Study limitations and continued research

This research has certain limitations. First, it included a small number of participants, meaning that future research can consist of larger samples to see if the results are the same.

Researchers were further limited by their inclusion and exclusion criteria, such as only working with participants who could communicate in English and did not have a history of certain conditions. They also did not include anyone who already had cognitive deficits and did not have a sedentary control group. Having this control group would have helped with looking to see if social interactions had an effect on hippocampal functioning. Since the research included healthy older adults who could engage in these exercise interventions, it’s unclear if the intervention would be possible in people with more health challenges.

Researchers further acknowledge that more research is required to understand if exercise affects working memory and the observed differences seen in the high-intensity interval group. Finally, researchers acknowledge that it’s unclear if similar methods of high-intensity interval training would produce the same results, so this may also be a focus of future research.

Study author, Dr. Daniel G. Blackmore, PhD , from the University of Queensland Brain Institute, noted the following areas for continued research:

“There are so many avenues that future research in this area can take. We have shown that it is critical to have a highly controlled exercise intervention with multiple parameters needing to be taken into consideration. The use of biomarkers as a diagnostic tool for exercise needs further research and we are now also looking at the genetic factors that may regulate a person’s response to exercise to see if we can establish who will and who will not respond to this intervention.”