The simple 1-minute test that reveals your brain’s true age, according to science

It might sound strange, but time doesn’t tick the same for everyone – at least when it comes to biology.

Some people really do age faster than others, meaning that the number of laps you've done around the Sun doesn’t always match what’s going on inside your cells.

That mismatch is known as your biological age, and it’s increasingly seen as an accurate predictor of health and longevity.

“Broadly, one might think of age in two ways: chronological and biological,” explains Prof David Sharp, a neurologist at Imperial College London. “Some people look much younger than their chronological age, and some people much older.”

Scientists once applied this idea to whole organisms. But now, they're taking a finer-grained view of ageing.

“The interesting direction of travel in this space is the ability to look not just at the whole person, but at individual organs,” Sharp adds. “So you might have a heart age and a liver age and a brain age, and they may influence whether you develop heart, liver or brain problems.”

Of all the organs researchers can now measure the biological age of, it’s perhaps no surprise that the brain – our body’s command centre – plays a powerful role in our overall health.

For instance, one recent study of 45,000 people found that those with biologically ‘older’ brains (that is, brains showing signs of ageing beyond what's typical for their chronological age) had a 182 per cent i ncreased risk of death by any cause over 15 years.

That research, published in Nature Medicine, gauged brain age by calculating a complex profile of proteins in their blood. But there are other methods. Researchers like Sharp are using neuroimaging techniques (including MRI, or magnetic resonance imaging, scans) to estimate the years between your ears.

“You can scan someone’s brain and see how the structure and size change as they age,” Sharp says. “They typically shrink somewhat as you get older, which leaves little spaces between the brain’s structures.”

Sharp’s work has found that having an older brain age is linked to weaker grip strength, poorer lung function, slower walking speed, lower intelligence and increased risk of death, among other things.

But what if, like most of us, you don’t happen to have an MRI machine in the garage? If brain age matters this much, wouldn’t it be helpful to get a sense of where you stand?

As it happens, there are a few science-backed ways to gauge how old your brain really is, from the comfort of your own home.

1. Test your walking speed

Walking might seem purely physical, but it also offers surprising insights into your brain health. And the tools to measure those insights are simple: a stopwatch, a tape measure, and a bit of clear floor space.

There are two versions of the test, depending on how much space you have. Indoors, measure out 1m (3.3ft) to give yourself a short lead-in, followed by a 4m (13.1ft) stretch where you actually time your walk.

Outdoors, you can go longer – 5m (6.4ft) to get up to your natural walking pace and 10m (32.8ft) for the timed portion.

Walk at your normal, comfortable pace and divide the timed distance in metres by the number of seconds it took you to cover it. That’s your gait speed.

Now here’s why it matters. In a long-running study of 1,000 people in New Zealand, researchers found that how fast someone walked at age 45 was a remarkably strong indicator of how quickly their brain and body were ageing.

“It's such a simple thing, walking," says Dr Line Rasmussen, lead author of the study. "But actually it relies on so many different organ systems and you need to coordinate the function of each of those systems – like muscles, vision, cardiorespiratory systems, your brain activity and so on. And that's why I think it is an indicator of ageing.”

People with slower walking speeds, Rasmussen and her colleagues found, weren’t just moving less briskly. They also had smaller brain volumes, thinner outer brain layers, and showed more signs of general wear and tear on brain scans.

Their cognitive test scores were lower, too, particularly for memory, reasoning and processing speed. On average, the slowest walkers had IQs 16 points below their zippier peers.

Your walking speed is even an indicator of how long you’re likely to live. Another study by researchers at the University of Pittsburgh found that for men aged 75, those with the slowest walking speeds had a 19 per cent chance of living for at least another 10 years, compared with 87 per cent for the speediest steppers. For women, 10-year survival was 35 and 91 per cent for the slowest and fastest walkers, respectively.

If you want to see how your walking speed stacks up for your sex and age (if you're 40 or above), use the table below to compare your results.

Women

40–49: 1.39 metres per second (about 3.1 mph / 5.0 km/h)
50–59: 1.31 m/s (about 2.9 mph / 4.7 km/h)
60–69: 1.24 m/s (about 2.8 mph / 4.5 km/h)
70–79: 1.13 m/s (about 2.5 mph / 4.1 km/h)
80–89: 0.94 m/s (about 2.1 mph / 3.4 km/h)

Men

40–49: 1.43 m/s (about 3.2 mph / 5.1 km/h)
50–59: 1.43 m/s (about 3.2 mph / 5.1 km/h)
60–69: 1.34 m/s (about 3.0 mph / 4.8 km/h)
70–79: 1.26 m/s (about 2.8 mph / 4.5 km/h)
80–89: 0.97 m/s (about 2.2 mph / 3.5 km/h)

Of course, it’s not just your brain that affects how briskly you walk – plenty of other factors come into play.

“It’s important to stress that while people can go and test their own gait speed, they need to remember that there is some variation,” Rasmussen says. “So it might point to something, but it’s not necessarily true that you need to be concerned if you walk slowly.”

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2. Measuring your reaction time

Reaction time – how quickly you respond to a visual or auditory signal – might seem like a relic from your driving test, but it’s actually one of the most sensitive indicators of how well your brain is functioning.

In simple reaction time tests (for example, tapping a button the moment a light appears), adults tend to slow down by around 2 to 6 milliseconds per decade. That might not sound like much, but over time, it adds up, and changes in your baseline can be more telling than any single measurement.

“What’s interesting is to see where you are in 10 years from now, given the current set-up of factors that you carry,” says Dr Anna-Katharine Brem, a senior researcher at the Centre for Healthy Brain Ageing at King’s College London.

“So starting at 50 or whatever, it doesn’t really matter, you can get a whole trajectory for a single person, and then you can see if something significantly changes within that normal range of functioning.”

In other words, the absolute number isn’t as important as the trend. If your reaction time suddenly slows well beyond the expected rate, it could be a sign of trouble – especially since reaction time draws on multiple brain systems working in concert, including attention, processing speed and motor control.

You can measure your reaction time using a range of free tools available online or in app stores. Highly rated options include Reflex & Reaction Time Test (on Apple devices), and SwitchedOn (on Apple and Android devices). For a quick browser-based test, try Human Benchmark – it lets you see how your performance compares with over 81 million other clicks from users.

Many use simple click-based setups: a shape changes colour or a stimulus appears, and your job is to tap or click as quickly as possible.

Whatever tool you use, it’s best to stick with the same tool each time if you’re interested in tracking changes over the long term.

Like gait speed, reaction time is easy to test at home, sensitive to subtle changes, and closely linked to brain health. It won’t give you an exact brain age, but a decline in your score over time can serve as an early warning sign.

Hands holding a smartphone. — Many reaction time tests can be carried out in seconds using a smartphone. - Getty

3. The spatial navigation test

Our brains are remarkably good at giving us directions. It’s why most of us don’t need much help finding our way to the local supermarket and back again.

But building an internal map from memory, rather than relying on familiar landmarks or cues at each turn, requires a more complex form of brain processing.

“Spatial navigation is a very early indicator of things like Alzheimer’s because it's associated with those areas of the brain that deteriorate first,” Brem says.

While a loss of navigation skills may not be indicative of all dementias, plenty of research has shown it is significantly associated with ageing.

“When navigating in unfamiliar environments,” explained neuroscientist Prof Scott Moffat in a review of the topic, “older individuals generally perform more poorly than younger participants, and elderly people with early-stage dementia perform more poorly than both normal older and younger participants.”

They also struggle to develop mental 'cognitive maps' – internal representations of space – and find it harder to use real maps to get around.

There’s no gold-standard home test for spatial navigation just yet, but one simple technique is to draw a freehand map from memory – say, from your house to the nearest train station, post office or café. Try to include as many details as you can: turnings, landmarks, road names, distances.

Over time, if your mental maps become fuzzier, or you notice you're relying more heavily on external cues to get around, it might be a subtle sign that your brain’s navigational systems aren’t running quite as smoothly as they used to.

4. The online brain check-up

“There’s nothing new about cognitive testing,” says Sharp. “What is new is that now you can do it on the internet.”

Thanks to smartphones, cognitive assessments that once required lab equipment and a trained psychologist can now be done from the comfort of your sofa. A quick search in the App Store or Google Play will turn up dozens of brain-training games and quizzes promising to boost or benchmark your mental fitness.

However, while such tests may be good to see how your mental abilities measure up, research suggests that using them regularly is unlikely to improve your cognition.

If you are looking for something backed by real science, Sharp recommends Cognitron – an online platform used in multiple academic studies and by over 500,000 people so far. The full test takes about 30 minutes and evaluates different aspects of brain function, including memory, attention, reasoning and processing speed.

At the end, you’ll get a breakdown showing how your performance compares with people your age. It won’t give you a definitive biological brain age, but it can offer a useful snapshot of how sharp your thinking is right now – and which areas might be worth keeping an eye on.

Keep in mind that results can be influenced by factors like education, sleep, stress and mood, so it’s best viewed as a starting point rather than a diagnosis.

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About our experts

David Sharp is a neurologist and centre director of the UK Dementia Research Institute Care Research & Technology, focusing on using technology to enhance the lives of people living with dementia. He is also scientific director of the Imperial College Clinical Imaging Facility and associate director of the Imperial Centre for Injury Studies.

Line Jee Hartmann Rasmussen is a senior researcher in the Department of Psychology & Neuroscience, Duke University, and the Department of Clinical Research, Copenhagen University Hospital Hvidovre. Her research integrates theory and methods from immunology, clinical research, and population-based studies to identify the risk factors, measures, and outcomes of systemic chronic inflammation with emphasis on its role in biological ageing and disease development.

Anna-Katharine Brem is a senior researcher at the Centre for Healthy Brain Ageing at King’s College London and a group leader at the Department of Old Age Psychiatry at the University of Bern, Switzerland. Part of her research focuses on the application of digital technologies in ageing and neurodegenerative diseases.