Fitness gains tracked sharper thinking in over-55s

Physical activity is well established as useful for healthy ageing, and there has long been a hope that it also protects thinking as we get older. The specific question is harder than it looks: aerobic training reliably improves cardiovascular fitness, but nobody has shown that this particular kind of fitness is the ingredient that helps the brain. If it is not, then any form of movement might do just as well. Studies that report activity, fitness and cognition in the same people are the way to start untangling this, and that is what this review gathered.

The reviewers searched MEDLINE, EMBASE, PEDro, SPORTDiscus, PsycINFO, CINAHL, the Cochrane Controlled Trials Register, dissertation abstracts and ongoing trials registers on 15 December 2005, with no language restrictions. They included published randomised controlled trials comparing aerobic physical activity programmes with any other intervention or with no intervention, in participants older than 55 years of age without known cognitive impairment. Eleven randomised controlled trials met the criteria, and two reviewers independently extracted the data. Outcomes spanned cardiorespiratory fitness, measured via maximum oxygen uptake, alongside a range of cognitive domains including memory, attention, processing speed and motor function.

Eight of the 11 studies reported that the aerobic intervention raised cardiorespiratory fitness in the intervention group by approximately 14%, as judged on the maximum oxygen uptake test, and those fitness gains coincided with improvements in cognitive capacity. The largest cognitive effects were on motor function (effect size 1.17), auditory attention (0.52) and delayed memory (0.50), with moderate effects for cognitive speed (0.26) and visual attention (0.26). Crucially, the majority of the comparisons made across these trials yielded no significant result, and the delayed memory finding comes from a single study. The review could not establish that the cognitive improvements were caused by the improvement in cardiovascular fitness.

This supports the broad idea that aerobic activity is good for some aspects of cognition in healthy older adults, while showing how patchy the effect looks once you inspect it domain by domain. It leaves the central mechanistic question unresolved: the temporal link between fitness gains and cognitive gains is suggestive, but larger trials are needed to say whether the aerobic component is necessary or whether any physical exercise would produce the same result. A second open question is why certain cognitive functions appear responsive while others seem untouched. The authors also flag that inconsistent cognitive test batteries across studies make results hard to compare and reproduce.

This is a reason to think aerobic activity in later life is associated with better performance in several cognitive domains, not a reason to expect an across-the-board mental upgrade. The unevenness matters: many comparisons found nothing, so anyone expecting a uniform effect on memory or attention is reading more into the evidence than it holds. It also remains unclear whether the fitness improvement is the active ingredient, which means there is no basis here for favouring aerobic work over other kinds of movement for brain reasons specifically. What survives is a modest, plausible link worth knowing about.