Exercise may not protect the ageing brain, big study finds

In the LIFE-Adult Study, involving more than 2,500 participants, researchers found no evidence that greater levels of physical activity led to larger hippocampal volume or better cognitive test scores. The hippocampus is the brain structure critical for memory and spatial orientation. Earlier, smaller studies had suggested exercise could enlarge it. The researchers published their findings in eLife.

Reverse causation

Even more striking: longitudinal analyses suggested the relationship may run in the opposite direction. People with a higher BrainAGE (a measure of how much older the brain looks than chronological age would suggest) were less physically fit at follow-up, not the other way around. That points to reverse causation: it is not exercise that keeps the brain young, but an older-functioning brain that leads to less physical activity.

The researchers also identified an age-related bias in self-reporting. Older participants systematically overestimated their own activity levels. This complicates the interpretation of any study relying on questionnaires rather than objective measurement.

What does this mean in practice?

The study does not disprove that exercise is beneficial. It does suggest that the protective effects on brain structure are less straightforward than long assumed, and that interventions may need to start earlier in life. The researchers suggest that future studies should target middle-aged adults rather than older populations.

For longevity science, this is a useful corrective. Many recommendations about exercise and brain health rest on smaller or observational studies. This large cohort adds a critical note to the consensus that had developed.

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