Less than 4 minutes of vigorous exercise a day could halve your dementia risk

Less than 4 minutes of physical exertion a day – such as rushing for the bus or carrying heavy shopping – could halve your dementia risk. People who engaged in short bursts of vigorous movement were up to 48 per cent less likely to develop the condition than their sedentary counterparts in a large study.

“These brief bursts of higher-intensity daily activities are in every nook and cranny of our day-to-day routines, so this creates a really exciting and viable opportunity to find new ways for the everyday person to protect their health,” says Nicholas Koemel at the University of Sydney, who parks his car in a distant space when he gets to work so he has to walk further.

Exercise brings a myriad of benefits, from promoting muscle growth and staving off cardiovascular disease to enhancing mental health. Yet many people find it hard to fit the recommended 150 minutes of moderate-intensity physical activity per week into their routines.

This has caused interest to grow in the benefits of the incidental exercise people get through ordinary exertion, like walking up a hill or playing energetically with children. Recent studies have found that such short bursts of activity can help keep your heart healthy and add years to your life. When it comes to cognition, just a couple of minutes of walking or stretching every hour has been linked to improved memory and attention span.

Focusing on dementia risk, Koemel and his colleagues analysed data from 22,618 adults, who were mainly in their early 60s, from the UK Biobank study. None of the participants had a dementia diagnosis when they strapped on wrist-worn accelerometers to track their activity over seven days between 2013 and 2015.

The researchers looked in the data for sporadic instances of high-intensity effort, such as climbing stairs, carrying heavy shopping or rushing for the bus. The participants were followed for around eight years after they wore the accelerometer until whichever came first: a dementia diagnosis, death or the end of the follow-up period in November 2022.

During the study, 170 of the participants were diagnosed with dementia. The researchers found that 2.5 per cent of those who did no exercise at all developed the condition. Among people who didn’t set aside time to exercise, but managed a few daily bouts of vigorous lifestyle activity, 0.71 per cent developed dementia. The risk was lowest, at 0.59 per cent, among those who deliberately exercised alongside their daily exertions.

Overall, an accumulation of just 3.7 minutes per day of vigorous routine movement was associated with a 48 per cent lower dementia risk. It was also linked to larger volumes of grey matter in several brain regions, and shrinking of areas of abnormal brain tissue known as white matter hyperintensities. “The results are pretty headline-grabbing,” says Mike Trott at the University of Queensland in Australia.

The study is observational, so it doesn’t prove that bursts of activity directly change dementia risk. It is also possible that undiagnosed dementia caused subtle functional decline that left some people less able to engage in such exercise, says Koemel. Another potential issue is that the study only covered a week-long snapshot of physical activity years before the dementia diagnoses, says Trott.

But previous studies show that, as cardiorespiratory fitness increases, dementia risk drops and grey matter volume increases. “The more we take care of our cardiometabolic health via activities like physical activity, the more we may prolong the health of our brain,” says Koemel.

The researchers speculate that even tiny vigorous bursts of activity could contribute to better vascular health by lowering blood pressure and reducing arterial stiffness. This reduces the chance of vascular brain injury, which can cause dementia. Energetic physical activity also often requires fast posture adjustments, which means engaging the brain’s cerebellar and sensorimotor networks. This could contribute to the larger grey matter volumes observed in these areas.

But the results don’t mean everyone should suddenly start running up the stairs. “We typically will recommend people gradually increase their physical activity, because radical shifts could increase the risk of certain accidents or injuries,” says Koemel. “A core message is that a little can go a long way here.”