Even light activity such as household chores might help to keep the brain young, researchers say, adding to a growing body of evidence that, when it comes to exercise, every little bit helps.
The findings mirror upcoming guidance from the UK chief medical officers, and existing US guidelines, which say light activity or very short bouts of exercise are beneficial to health – even if it is just a minute or two at a time – countering the previous view that there was a threshold that must be reached before there were benefits.
“Our study results don’t discount moderate or vigorous physical activity as being important for healthy ageing. We are just adding to the science, suggesting that light-intensity physical activity might be important too, especially for the brain,” said Dr Nicole Spartarno first author of the study from Boston University, adding that light activity might include a gentle walk or household chores.
Writing in the journal Jama Network Open, the international team of researchers report how they made their findings by studying at least three days of activity-tracker data from 2,354 middle-aged adults from the US, together with the participants’ brain scans.
From the latter, the researchers worked out individuals’ brain volume, a measure linked to ageing: about 0.2% of the volume of the brain is lost every year after the age of 60. Loss or shrinkage of brain tissue is linked to dementia, Spartano noted.
After taking into account factors including sex, smoking status and age, the team found that every extra hour of light physical activity per day was linked to 0.22% greater brain volume, equal to just over a year’s less brain ageing. What’s more, those who took at least 10,000 steps a day had a 0.35% greater brain volume than those who took, on average, fewer than 5,000 steps a day – equivalent to 1.75 years’ less brain ageing.
The results were even starker when the team looked at those who did not meet recommended guidelines for physical activity – just over half of the participants.
While the results also suggested greater levels of moderate to vigorous physical activity were linked to higher brain volumes, the team say further analysis suggests this could just be because these people were also doing more light activity.
But Spartano said, even if true, that did not mean people should stop trying to break a sweat. “Higher levels of fitness are linked to longevity and a better quality of life in older age, not to mention being associated with lower rates of dementia,” she said.
However the study has limitations: it is based on a snapshot in time, mainly white participants, and cannot prove cause and effect – those with more brain ageing might move less. The authors add that not all time spent sedentary is necessarily “bad” for the brain – particularly if people are engaged in a task that takes a lot of thinking.
Emmanuel Stamatakis, professor of physical activity, lifestyle, and population health at the University of Sydney welcomed the overall message, but questioned some of the results.
“The finding that even light-intensity physical activity, that it is usually part of daily living, is associated with brain volume is very encouraging as such activities are feasible for most middle-aged and older people, even those who are less likely to do structured exercise,” he said.
But, he added, there was no biologically plausible reason moderate to vigorous activity would have less effect on brain volume than light activity. For cardiovascular health, said Stamatakis, a minute of high-intensity activity was known to be more beneficial than a minute of light activity.
Dr James Pickett, head of research at Alzheimer’s Society, stressed the research did not look at the impact of different levels of activity on dementia risk, although it is known that, in general, exercise reduces the risk of such conditions.
“Don’t worry if you’re not hill-running, but find something you enjoy and do it regularly, because we know that what’s good for the heart is good for the head,” he said.