The team found evidence that cognitively healthy octogenarians continued to generate new neurons — a process known as neurogenesis — in the hippocampus, a brain region involved in learning and memory.

Whereas in the brains of older people who had cognitive decline or Alzheimer’s disease neurogenesis had slowed, the super-agers produced twice as many neurons as healthy adults with normal memory of the same age. The super-agers were found to have an added, distinct “resilience signature” — a cellular environment that supports the survival of new neurons — in their hippocampi, which set them apart.

The study is the first to identify a genetic difference between people whose brains withstand age-related cognitive decline and those whose don’t.

“Determining why some brains age more healthily than others can help researchers make therapeutics that will boost memory in ageing and prevent Alzheimer’s disease and related dementia,” says Orly Lazarov, associate professor of neuroscience at the University of Illinois, Chicago.

Tamar Gefen, associate professor of psychiatry and behavioural sciences at NU, who was a co-author on the paper, says the findings provide “biological proof that their brains are more plastic, and a real discovery that shows that neurogenesis of young neurons in the hippocampus may be a contributing factor”.

Not all of us will become super-agers. Gefen says that super-ageing occurs partly because of better neurogenesis, but also “because there is a type of genetic programming” that allows for the preservation of new neurons.

However, previous research by the Northwestern team has shown that age-related brain changes can be linked to lifestyle factors, such as wide friendship groups and close social connections. So, how best can we prepare to have razor-sharp memories as we age? We asked the experts:

Always try to walk a few more steps (at a faster pace)

Walking has a powerful impact on ageing and Professor Salvador Macip Maresma, who researches thermolecular aspects of ageing at the Universitat Oberta de Catalunya, in Spain, says that most of the super-agers he has encountered clocked up considerable daily steps as part of their active lives. “Doing so has been shown to amplify blood flow to the brain,” he says, with some studies demonstrating that just 20 minutes of walking most days from middle age onwards is enough to boost fitness to a level that will lower the risk of dementia.

Try one new thing each day

Monotony and lack of stimulation are the worst for brain sharpness. “Neuroplasticity — a scientific term for how the brain changes with learning — only occurs when there’s challenge and struggle and novelty in the things we do,” says Dr Sabina Brennan, a neuroscientist and assistant professor at the Trinity College Institute of Neuroscience in Dublin. “We need to try new things for our brains to become better at focusing and remembering.”

Even tiny tweaks to your day can improve brain health, with scientists at the University of Toronto revealing how “experiential diversity” — trying new things every day — can boost memory. “Ideally, there should be an element of challenge, so doing Sudoku won’t help much if it is too easy for you,” Brennan says. “But trying a new dance routine, learning the names of the plants while you garden, will all help with brain attention and focus.”

Keep in touch with friends (or make new ones)

Humans thrive on social interaction, so a key aspect of healthy brain ageing is to maintain a good social circle and mix with people of different ages.

“There is a proven biological effect, as we see older people without a strong social network go downhill very quickly,” Marasma says. Psychologists reporting in the Epidemiology and Psychiatric Sciences journal confirmed, in an eight-year study, that from mid-life onwards, adults with strong social networks were 24% less likely to die prematurely.

Go for a five-minute jog or an outdoor swim

A brisk walk, a short outdoor swim, or a jog around the local park — in fact, any activity that raises your heart rate for as little as five minutes at a time — is a route to better brain health, says Dr Maddison Mellow, a neuroscientist at the University of South Australia. He reviewed data on 585 adults in their 60s and older and found a direct link between regular moderate-to-vigorous intensity exercise and better brain-processing speed and working memory.

“Specifically, ‘huff-and-puff’ physical activity (like aerobic exercise) improves processing speed (how fast your brain thinks), executive function (how well you plan, focus, and multi-task), and working memory (your ability to store information for short periods of time),” Mellow says.

Eat for a healthy brain

The brain is a high-energy organ and depends on the food you eat to provide energy for its cells. “It has to manage the resources available to meet the tasks,” Brennan says. “It needs to know when food and nutrients are coming next, so regular meal times and a variety of nutritious food — colourful veg, oily fish, and wholegrains — are important to keep the brain functioning well.”

One study, from the University of North Carolina, found that eating high-fat junk food disrupted memory circuits in the brain almost immediately, with neurons in the hippocampus becoming overactive — and impairing memory — within just four days.

Get regular sleep

Sleep is critical for brain health as we age. “When we go to sleep, our brain doesn’t sleep, it has work to do, including a deep cleaning that gets rid of any metabolic toxins and waste,” says Brennan.

During sleep, electrical activity between the hippocampus and the frontal lobes filters new information taken in during the day. “When you wake up with a clearer focus and even a solution to a problem, it is because your brain has been making connections during the night,” she says.

Her tip is to get up at the same time every morning. “That will help train you towards a more regular bedtime at night,” Brennan says. “And your sleep hours will be better regulated.”

Train your brain to focus by reading a book

You can rebuild your mental stamina and ability to focus by setting aside time for long-form reading, instead of skimming on your phone. “There’s evidence that we absorb things much better when we have read them in print form,” Brennan says. “Whereas online reading is fine for harnessing key points, for a deeper understanding and focus on something, we should train our brain to read printed pages for longer periods.”

Trying a new dance, learning the names of the plants while you garden, will all help with brain attention and focus