The routine activity that can tell how old your brain is

 

The speed at which you walk can reveal profound insights into your brain's rate of ageing – with slower walkers having smaller brains and fundamental differences in crucial structures.

 Although it may appear insignificant, how quickly you can walk from A to B can reveal a lot about your mind and body. According to research, your likelihood of being hospitalized, having a heart attack, or even passing away can be predicted based on how quickly you walk to the bus stop, the local park, or the shops. In fact, a person's gait speed can even be used to reveal their rate of cognitive ageing.

 The walking speed test is a way of assessing someone's functional capacity –  their ability to perform daily tasks around the house and maintain independence.  It can also reveal how frail a person is, and predict how well they will respond to rehabilitation after a stroke.

 Even though it's normal for people to walk slower as they get older, a sudden drop in a person's gait speed could mean that something more serious is going on. Christina Dieli-Conwright, a Harvard Medical School professor of medicine who studies the effects of exercise on cancer prognosis, says, "When a person's normal walking pace declines, it is often associated with underlying health declines."

"It might be that the person has a chronic condition which has meant that they haven't been moving as much or have become sedentary.  That means that, more than likely, they've experienced a decrease in muscle strength, and joint mobility, which unfortunately leads to further health declines," says Dieli-Conwright.

 A simple technique

 To perform the walking speed test, all you need is a stopwatch and a way of measuring distance, such as a tape measure.  There are two typical variants. If you are outside and you have lots of space, you could try the 10m (33ft) walking speed test.  First, measure out 5m (16.5ft), followed by another 10m.  To get started, it's recommended to walk for 5m to get up to your normal speed, then walk at your normal pace for 10m.  Simply divide 10 meters by the number of seconds it took to walk that distance to determine your walking speed.

If you're at home and space is more limited, you could try the 4m (13.2ft) walking speed test.  With this test, measure out 1m (3.3ft), followed by 4m.  The idea is to use the first metre to get up to speed, then time how long it takes to walk for 4m at your usual pace.  To work out your speed, divide four metres by the number of seconds it took you to walk that distance.

Alternately, you can measure your walking speed with a variety of apps, such as fitness trackers like Walkmeter, MapMyWalk, Strava, and Google Fit. These apps use GPS to track distance and time to calculate your speed. Studies have shown that gait speed is a significant predictor of life expectancy in older adults.  For instance, researchers at the University of Pittsburgh compiled the findings of nine studies that followed more than 34,000 adults 65 and older who lived in the community and were between the ages of six and 21. The study demonstrated a strong correlation between lifespan and gait speed. Men with the slowest walking speeds, for instance, had a 19% chance of surviving for a decade at age 75, whereas men with the fastest walking speeds had an 87% chance of surviving for a decade. One possibility is that people who are already ill are less mobile. However, a 2009 French study found that participants with a slower walking speed were approximately three times more likely than those with a faster walking speed to die from cardiovascular disease during the study period. Line Rasmussen, a senior researcher at Duke University in North Carolina, claims that "walking seems like such a simple thing – most of us don't think about it, we just do it."

"But walking actually relies on many different body systems working together: your bones and muscles carry and move you, your eyes help you see where you're going, your heart and lungs circulate blood and oxygen, and your brain and nerves coordinate it all," adds Rasmussen. "But walking actually relies on many different body systems working together." According to Rasmussen, as we age, the function of these systems starts to slow down – and a slower walking speed can therefore reflect this overall decline and be a sign of advanced ageing.

 This doesn't just apply to older adults.  In a 2019 study, Rasmussen and colleagues found that, even amongst 45-year-olds, a person's walking speed could predict the rate at which their brain and body were ageing.