Physical Activity & the Aging Brain

A recent study published in Frontiers of Aging Neuroscience adds to the growing body of evidence suggesting that physical activity can protect the brain against aging and Alzheimer’s disease. Scientists compared older adults who engaged in high physical activity with those who engaged in low physical activity. All participants were healthy with no cognitive impairment, although some had the Apolipoprotein E4 (ApoE4) mutation, which raises the risk of Alzheimer’s disease.

In adults with the ApoE4 gene, high physical activity was associated with less shrinkage of the brain’s hippocampus over an 18 month period. An earlier randomized control study similarly reported that aerobic exercise could increase the size of the hippocampus and improve memory function in older adults. 

Why is this important? The hippocampus plays a critical role in memory function and is particularly vulnerable to Alzheimer’s disease. Some clinical observations suggest that a contracting hippocampus indicates a high risk of future cognitive problems in otherwise healthy older adults. If physical activity can protect the hippocampus from shrinkage, then perhaps it can delay the onset or reduce the risk of Alzheimer’s disease and memory impairment. 

Interestingly, high physical activity was only associated with less hippocampal shrinkage in people who had the ApoE4 genetic risk factor. While that result needs to be replicated in other studies, it aligns with other areas of research suggesting that some potential prevention therapies will be protective only in ApoE4 carriers or only in ApoE4 non-carriers.

Just how much physical activity is needed? Participants in these studies were classified as physically active if they engaged in moderate to vigorous physical activity three or more days per week. Activities included brisk walking, jogging, or swimming for 15 minutes or more; moderately difficult chores for 45 minutes; regular jogging, running, bicycling, or swimming for 30 minutes or more; and playing sports such as handball or tennis for an hour or more.

The takeaway of this study—exercise is beneficial, but you don't have to start training for a marathon.

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