The literature is full of myths about how to prevent brain aging. One of most durable is that exercise can delay or prevent the decline in cognitive function that typically comes with normal aging. This week, an article in The Journal of the American Medical Association – Neurology reported on an experiment to test the claim that cognitive decline can be prevented by exercising regularly or taking standard heart medications. For more than two years, 513 older adults exercised at moderate to vigorous intensity for nearly three hours a week. Another group of older adults did not exercise but took a standard regimen of statins and blood pressure medication. A third group of older adults did both. Finally, a fourth group did not exercise regularly and did not take the medications, essentially matching the experience of older adults in the US. The study found no significant cognitive benefit from any of it.
The study was conducted at four sites across the US. A total of 3290 individuals were screened, and 513 older adults (aged 60-85 years) without dementia and without hypertension, family history of dementia, and/or self-reported subjective cognitive decline were randomized. Sixty-three percent were females.
The main question was whether combining regular aerobic exercise with medications typically used to reduce cardiovascular risk would rescue brain health better than either intervention alone. Statins and blood pressure medications work via different mechanisms, as compared to exercising. The authors initially predicted that the benefits of these two approaches might synergize to reduce the risk of cognitive decline.
The study measured learning and memory abilities using the Preclinical Alzheimer Cognitive Composite and executive function using the NIH Toolbox Cognition Battery. After the two-year trial ended, the results showed that the groups doing regular exercise and/or taking the standard medications both improved to the same degree as the older adults who did not exercise or take any medications. The difference between the exercise group and the non-exercise group was statistically indistinguishable.
However, as predicted by numerous other studies, the adults who exercised maintained their cardiorespiratory fitness over two years while the control group’s fitness declined. The adults who took the two medications showed reductions in systolic blood pressure and LDL cholesterol; however, they showed a similar decline in cognitive function as the other three groups.
These results appear to contradict popular myths on the topic that are full of personal observational studies. Unfortunately, these claims always lack a true placebo group. Only randomized trials can demonstrate causality rather than just correlation, and those trials, when properly conducted, do not support popular myths. A recent review of the literature found that the apparent benefits of exercise on cognition largely evaporated after correcting for publication bias. The SPRINT MIND trial, which tested intensive blood pressure lowering in a large population, found no statistically significant improvement in cognitive test scores, either; though it did reduce the incidence of mild cognitive impairment and dementia when those outcomes were combined.
What makes this study so relevant is that it was designed to determine whether either intervention could improve or maintain cognitive performance in people who are still cognitively normal, which is most adults in this age range. Future studies involving more subjects are necessary to determine the role of practice effects on cognitive tests, the influence of poor diets, and the presence of biological markers of potential Alzheimer’s risk. The current evidence indicates that regular exercise alone, or medication alone, or the two together, is not enough. If you would like to learn about the various effects exercise has upon the brain, go here.
