Australasian Science: Australia's authority on science since 1938

Exercising the Brain

By Tim Hannan

Can physical activity in later life slow the rate of cerebral atrophy?

In 65 BCE, the Roman orator Marcus Cicero opined: “It is exercise alone that supports the spirits, and keeps the mind in vigour”. These days, the benefits of physical activity for general health, mood and cognitive functioning are well recognised – even if a consequence of the Ashes tour is that the attention many of us pay to physical activity at this time of year is more vicarious than actual.

However, a recent study offers a new incentive to challenge such sedentary preferences by proposing that physical activity may prevent deterioration in the ageing brain, and that the benefits derived from activity exceed those that accrue from engaging in complex mental activities.

Normal ageing has long been associated with the gradual shrinkage or atrophy of the brain, whether measured by overall volume, the volume of the gray matter of the cortex or the white matter of its connecting neural fibres. Some studies have found a decline of up to 10–15% of brain size, with the degree of atrophy associated with age-related decline in cognitive functioning and the onset of dementia. While found in the brains of all older individuals, atrophy is markedly reduced in those who are physically healthy.

Recently, Alan Gow and colleagues from the University of Edinburgh investigated whether engagement in regular physical activity was associated with the degree of atrophy observed in elderly individuals. The researchers took advantage of a longitudinal ageing study that, in 1947, assessed the intelligence of more than 1000 children born in 1936. Seven decades later the health status of 638 of these participants was reviewed, and they were surveyed regarding their engagement in physical activity, from basic chores and walking regularly to heavy exercise or competitive sports. Other leisure activities were also surveyed, including participation in mentally demanding tasks such as crosswords, reading books or self-education, as well as involvement in social activities.

The researchers obtained magnetic resonance imaging scans of participants’ brains to derive estimates of overall brain size and gray and white matter volumes. The findings, reported in the journal Neurology, were striking: participants who engaged in regular physical activity displayed less shrinkage of the brain overall, with higher volumes of both gray matter and normal-appearing white matter. The results were unrelated to participants’ general health status, or their initial IQ or social class.

The study’s authors were unable to offer a clear explanation why activity might reduce the rate of atrophy, but noted that by increasing blood flow to the brain, increased oxygen and nutrients are delivered to brain cells. It must also be noted that their study was correlational: it is possible that individuals with a higher rate of atrophy are less inclined to engage in physical activity, while those with healthier brains tend to be more active.

One fascinating finding was that engaging regularly in mentally challenging tasks or social activities was not associated with the degree of cerebral atrophy. While mental activities are often promoted as useful for keeping the brain in shape, participants who regularly pursued cognitive tasks or social activities displayed no slowing in the rate of brain shrinkage.

Several large projects over the past decade have found an association between exercise and the preservation of cognitive functioning, but the present study is the first to suggest that, for older individuals, benefits may accrue from physical activity involving modest energy expenditure, such as walking regularly.

The Edinburgh study does not demonstrate that mental tasks and leisure activities are of no benefit to older individuals, and indeed other studies have found that these activities play a major role in reducing the risk of depression and fatigue.

Further examination of the relative merits of physical and mental activity on the ageing brain requires longer-term studies utilising specific interventions. However, this preliminary work does suggest that older Australians inclined to exercise the mind through cryptic crosswords or puzzles would do well to cancel the home delivery and walk to the newsagent each day instead.

Tim Hannan is an Associate Professor of Clinical Psychology at Charles Sturt University, and the President of the Australian Psychological Society.