Aerobic Exercise Halts Age-related Cognitive Decline
Older adults who engaged in a 5-year training program scored higher on cognitive assessments that may predict the risk for dementia and cognitive impairment.
Welcome to this week’s installment of the Physiology Friday newsletter. Thanks for reading.
If you aren’t yet a subscriber to my Substack, please sign up below to receive my weekly newsletter along with updates on other posts I publish. My newsletter and posts are free (and always will be), but you have the option of a paid monthly or yearly subscription that helps to support the work that I do. If you enjoy my content and have the means to do so, please consider a paid subscription.
Links to a few cool discounts:
As always, thanks to the sponsor of this newsletter, LMNT electrolytes. Check out this tasty, sugar-free electrolyte drink mix and try some for yourself! Go to drinkLMNT.com/scienceandchill for a free sample pack (just pay shipping) or to replenish your stock of salt.
What are you more concerned about losing with age — physical strength or mental capabilities?
The discussion on aging and how to prevent it often deals with the physical effects of aging — a loss of muscle and strength, reduced agility, and increased difficulty doing activities of daily living. The study of aging also focuses on the physical ailments associated with it including cardiovascular disease and diabetes, among others.
But the brain gets old along with the body. Cognitive decline and the more serious ailments of mild cognitive impairment (MCI), dementia, and Alzheimer’s disease are quite common among the elderly, and rates seem to be rising around the modern world.
Is there a chance these declines in brain and body are related? Could age-related reductions in physical fitness cause reductions in brain health?
We know that many physiological pathways are shared by skeletal muscle, heart tissue, and neurons. This includes things like insulin signaling, glucose metabolism, inflammation, and mitochondrial function. It doesn’t seem too bold to consider that much of what we consider “normal” brain aging is simply the result of a neglected brain, to be sure, but also perhaps a neglected body.
Many studies have investigated the effects of exercise on cognitive function in healthy and aging individuals, so we have pretty convincing data that exercise is good for the brain. Furthermore, it is generally well known that individuals who are more physically active have higher brain function, especially at older ages. Generally, however, much of this data comes from observational or cohort studies.
One looming question is whether structured exercise could directly prevent or delay declines in brain health with age. Furthermore, what happens if one actually improves their fitness at an old age? Does cognitive function improve along with changes in fitness? If so, this could implicate cardiovascular health, and more specifically aerobic capacity, in the epidemic of cognitive decline we are seeing in our rapidly aging population — one that is all too often very sedentary as well.
There are very little longitudinal (i.e. long-term) data on how aerobic fitness influences brain aging. This is because of the obvious limitations and difficulties running exercise training studies of a year or more. Most studies are anywhere from 4 to 12 weeks in duration — much too short to really understand how aging might be playing a role on any outcome of interest.
Some of that data is now available and provides at least one piece of an ever-growing puzzle in how cardiovascular and brain aging may be related.
The data come from a large-scale longitudinal study known as the “Generation 100 Study.” This study — performed by a research group in Norway — included 945 participants (that’s a lot!) in a 5-year intervention of how exercise training affects morbidity, mortality and, specific to this discussion, brain aging.
Brief study methods
Studying aging is more useful when one actually studies “aging” individuals, which this investigation did. On average, participants were ~73 years old at baseline and ~78 years at the end of the intervention. Almost half of the participants were female, which is another strength, since it allows for an investigation of (potential) sex differences in exercise’s effect on aging. Males and females do not age at the same rate, and we shouldn’t expect them to respond to interventions in a similar way at older ages either.
During the 5-year study, participants completed an exercise intervention consisting of either high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT). There was also a control group who, while not given a specific exercise training plan, were advised to get the recommended weekly amount of physical activity. This may have had a not-insignificant effect on results of this study (more to come on this later!) Exercise for the assigned groups was completed twice per week.
The research team assessed cognitive function using something called the MoCA score (short for Montreal Cognitive Assessment). Higher scores on this test are better (the maximum score is 30), and scores below a certain predefined threshold are used to indicate or detect mild cognitive impairment (MCI).
Aerobic fitness (VO2 peak) was assessed at baseline and 1, 3, and 5 years of study involvement. Along with how exercise impacted aerobic fitness, this outcome was also used to analyze relationships between changes in VO2 peak and MoCA scores across time. For this outcome, the research team divided participants into 3 groups for analysis: those who increased their VO2 peak more than 3.5 ml/kg/min, those who maintained their VO2 peak (+/- 3.5 ml/kg/min change), and those whose VO2 peak decreased (more than a 3.5 ml/kg/min decrease).
Results
- At the end of the study, when participants were ~5 years older than baseline, the exercise groups had a higher VO2 peak compared to the control (non-exercise) group.
- However, when analyzed separately by high- and moderate-intensity training groups, only the HIIT group showed higher VO2 peak at the end of the study.
- None of the groups significantly increased their VO2 peak from baseline.
Let’s underscore that last statement. Across 5 years of aging, there was NO CHANGE in VO2 peak. This means that as a whole, the groups maintained their aerobic capacity despite being 5 years older. After age 30, it is typically known that VO2 peak declines about 10% per decade, meaning we might expect a 5% decrease over 5 years of aging and perhaps even more in the 8th decade of life. This would correspond to a ~2 ml/kg/min decrease in VO2 peak in this study, which was not observed. In this respect, the exercise interventions (and control) were effective at preventing the age-related decline in aerobic capacity.
- When the exercise groups were combined and compared to the control group, there were small but non-significant differences for MoCA scores and incidence of MCI — the adults who engaged in prescribed exercise had higher scores on the MoCA and lower odds ratio for MCI compared to the adults in the control group.
- When the groups were separated into HIIT and MICT and compared to the control group, exercise still produced higher MoCA scores and lower odds for MCI compared to the control group, but again, these findings were not statistically significant.
- There were no differences in cognitive assessment scores between the HIIT and MICT groups.
- Increasing VO2 peak during the 5-year intervention was associated with better MoCA scores and a lower odds ratio for cognitive impairment.
- Specifically, increasing one’s VO2 peak by 3.5 ml/kg/min increased MoCA score by 0.46 points and decreased the risk for MCI by 27%.
- Compared to those who maintained VO2 peak, those who increased VO2 peak more than 3.5 ml/kg/min had MoCA scores that were 0.24 points higher and odds for MCI that were 30% lower.
- Participants whose VO2 peak decreased more than 3.5 ml/kg/min had MoCA scores that were 0.64 points lower and odds for MCI that were 35% higher. It should be noted that neither of the above results reached statistical significance when an adjusted linear model was run.
- In males, exercise was associated with 0.8 points higher on the MoCA and a 32% lower odds ratio of MCI compared to the non-exercise group. There was no statistically significant effect observed in women.
Thoughts and musings
We’ve got to deal with the elephant in the room in that none of the above results (aside from those regarding sex differences) were significant from a statistical point of view. However, changes are changes, and we should respect the moderate improvement (or reductions) in cognitive assessment scores for what they are worth.
We also have to address the several limitations present in this study. The biggest flaw (in my opinion but also noted by the authors) regards the control group. This group was not given any specific exercise recommendations other than to “follow the recommended guidelines.” They did this unfortunately all too well. The control group was actually quite active throughout the 5-year study duration, having a high adherence to the physical activity guidelines and likely being almost just as active as either of the exercise training groups. For this reason, we can’t really say for sure that the exercise levels were different among the control, HIIT, and MICT groups.
It appears that over the course of a 5-year training intervention, beneficial changes in cognitive assessment scores and the reduction in MCI risk were only present in men. Why this is the case isn’t quite clear, but perhaps could be related to the higher overall risk for MCI in men compared to women; meaning exercise would exert a greater protective effect.
In summary, these findings reinforce what we already know — exercise is good for the brain. They also provide novel, direct evidence that cardiovascular health (fitness) is directly related to, and perhaps causal of, brain aging.
To reduce one’s risk of cognitive decline, engaging in exercise that stresses your system enough to either maintain or increase aerobic fitness is a must. It seems like 2 days per week borders on the edge of effectiveness, and I’d venture to guess that 3-5 days per week would exert potent effects.
Though participants in this study were older, the data are promising, and it’s never too early to start an “anti-aging” exercise routine. Building a strong aerobic base now that can be maintained into old age might ensure that your mind stays just as strong as your body.
Thanks for reading. See you next Friday.
~Brady~
Study cited
Create your profile
Only paid subscribers can comment on this post
Check your email
For your security, we need to re-authenticate you.
Click the link we sent to , or click here to sign in.