One long brisk walk may protect your brain from dementia and anxiety more than short walks put together

Exercise is well known for keeping the brain healthy, but does how we move matter as much as how much we move? In a recent study, researchers investigated whether sustained periods of physical activity offer greater long-term protection against dementia, depression and anxiety than the same amount of activity spread across shorter bursts.

More than 66,000 people contributed movement data through the UK Biobank. Each person wore a device around their wrist, similar to a fitness tracker, for one week, providing an objective measure of daily activity. Their health was then tracked for an average of 7.5 years using hospital records to identify later diagnoses of these conditions. The findings are published in Translational Psychiatry.

Those who engaged in longer, uninterrupted periods of physical activity had a significantly lower risk of developing dementia, depression or anxiety later on. Doing just 13 minutes of moderate-to-vigorous physical activity (MVPA), such as a brisk walk, in one continuous session was linked to a 72% lower risk of dementia.

The way people accumulate their daily activity appears to matter for future health. People whose activity was least broken up had an 82% lower risk of dementia, a 57% lower risk of depression and a 52% lower risk of anxiety compared with those whose activity was most broken up. Such sustained activity also went hand in hand with a healthier brain, including larger left hippocampal volume, a brain region tied to memory, and fewer signs of small blood vessel damage on brain scans. These associations were seen regardless of how much total physical activity people did overall.

Protective effects of long movements

Moving more is one of the simplest ways to support a healthier brain, as it has been consistently linked to better cognitive health and a lower risk of mental health conditions. The World Health Organization recommends 150 to 300 minutes of moderate-to-vigorous physical activity each week for better brain health.

Current guidelines tell us how much exercise to aim for, but they don't say whether it's better to get it done in one longer session or spread it out through small bursts of movement.

Previous studies using wearable trackers have hinted that more continuous activity may be better for heart health and longevity. But whether these different movement patterns influence brain conditions such as dementia, depression or anxiety has remained largely unknown.

To get a clearer picture, researchers tracked how a large group of people moved each day, then followed their health for several years to see how those patterns affected the brain.

Everyone was between the ages of 40 and 69, with no prior diagnosis of dementia, depression or anxiety. Each wore a wrist device that captured movement 100 times per second, picking up even tiny shifts in activity.

The researchers looked for three parameters: the longest continuous stretch of general movement, MVPA bouts and activity fragmentation. They used official hospital and national health records to see who was eventually diagnosed with the conditions. For a smaller group of 13,108 participants, researchers also used MRI scans to examine brain structure.

The data revealed that the pattern and continuity of movement are just as important for brain health as the total amount of exercise. Even if recommended weekly minutes of activity were met, doing so in longer, continuous stretches provided significantly more protection than short, sporadic bursts.

To get the maximum benefit for mental health, the researchers found a sweet spot of 36 minutes of continuous brisk activity, which was linked to a 52% lower risk of depression and a 50% lower risk of anxiety. Brain scans showed that people with the most broken-up (highly fragmented) movement patterns had lower total brain volume compared with those who moved more continuously.

The researchers also wanted to see whether exercise patterns helped certain people more than others. They used blood samples to identify carriers of the APOE4 gene, a known genetic risk factor for Alzheimer's.

For people without the APOE4 gene, longer stretches of uninterrupted activity lowered dementia risk, but only up to a point, after which the benefit plateaued. For carriers, however, dementia risk kept dropping as their activity became more continuous, with no sign of leveling off.

Dementia, depression and anxiety are among the most serious public health concerns, and this study's findings point to a low-cost, accessible way to reduce the risk of developing these conditions.

Health campaigns could change their message to match the results. Instead of just telling people to hit a weekly activity target, they could encourage those who can to fit one sustained brisk walk, bike ride or similar continuous activity into their exercise regimen.