Six ways to keep your brain sharp as you age

Our brains start to shrink in midlife, but some behavioural habits can play an outsized role in accelerating age-related cognitive decline, giving us more control than we might think,

From the age of 40 onwards, the brain begins to steadily shrink in size with every passing decade. Picture: iStock

Forgetting someone’s name or where you left the car keys is a normal, if frustrating, part of the cognitive changes that can start to happen in midlife.

From the age of 40 onwards, the brain begins to steadily shrink in size with every passing decade, while in our 60s, we start to lose some of the connections between distant parts of the brain. This all means that our thinking and decision-making are not quite as sharp as they once were.

But the rate at which the brain ages is also highly individual and varies greatly from one person to the next, and we’re increasingly learning that certain behavioural habits play an outsized role in accelerating brain ageing.

Let’s take a look at some of the key habits to avoid and what to do instead.

1. Excessive passive screen time

With more and more of us spending our evenings and weekends scrolling through social media on our phones, experts are concerned about the long-term neurological impacts of excessive passive screen time.

“Screen use, particularly late at night, may interfere with sleep,” says Sabina Brennan, a neuroscientist at Trinity College Dublin, and author of 100 days to a younger brain. Such concerns have traditionally been linked to too much TV. Research has suggested that watching four or more hours of television per day is linked to a significantly greater risk of developing cognitive impairment. Brennan believes that the same may apply to passively viewing content on our phones.

Sabina Brennan: Social interaction is deeply stimulating for our brain, even an ordinary conversation can make all the difference.

So-called ‘doomscrolling’, she says, can increase stress and anxiety levels due to repeated exposure to threatening or upsetting content, while viewing a rapid succession of disconnected posts fragments our attention spans.

The fix: Step back and consider your screen-based activity. Brennan points out that not all screen time is equivalent. In particular, if you’re spending that time connecting and communicating with others, or actively learning new information, it’s likely to have a very different effect on your brain.

“Reading, learning, creating, working, or connecting meaningfully with another person may involve far more mental activity than passively consuming content,” she says.

2. Prolonged sitting

Spending too much of your waking day in a sitting position is one of the worst things for accelerating your risk of cognitive decline, especially as you get older. Over-60s who spend more than nine hours per day sitting have been found to have a much greater risk of dementia in the following seven years.

Brian Lawlor, professor of old age psychiatry at Trinity College Dublin, says that this is because when you’re moving, a protein is released in the brain which promotes connections between nerve cells. “When you’re sitting, you’re not moving,” he says. “Spending a lot of time commuting, sitting at a desk, and looking at screens may be damaging to brain health. So we need to be mindful not just of increasing our physical activity levels, but reducing our sedentary behaviour.”

The fix: Experts recommend trying to find ways to break up long periods of sitting, for example, by taking a few minutes to walk around the house or office, or by making deliberate choices to be active when you have the opportunity.

“If a sedentary lifestyle is a part of your life, try and counter it by getting off the bus before your usual stop and walking the rest of the way home,” says Lawlor. “The key is to reduce the number of hours of passive sitting time.”

3. Smoking and possibly vaping

Brain imaging studies have long shown that smokers tend to have smaller brain volumes than non-smokers, while smoking is known to affect white matter, the tissue that transmits signals quickly through the brain. Disruptions to white matter can affect attention, speed of thinking and memory.

Garret McDermott, a clinical neuropsychologist at the Institute of Memory and Cognition at Tallaght Hospital, says that this is because the carbon monoxide, tar and other chemicals generated by the burning of tobacco have a direct effect on the health of your blood vessels, and how well your breathing system works.

“The brain depends on these systems directly for its health,” he says.

The fix: If you are an existing smoker, then vaping is thought to be a better option. However, McDermott says that data on the impact of vaping on the brain is still emerging, and ingesting large quantities of nicotine is unlikely to be good. “Nicotine is known to increase blood pressure, increase heart rate, and narrow blood vessels,” he says. “These are all known to be bad for long-term brain health. The evidence that is out there suggests that stopping both smoking and vaping is the best option for brain health.”

4. High sugar intake

While sugary foods may be one of life’s great treats, consuming an excess of added sugars in particular — the kind found in fizzy drinks or in chocolate bars and cakes — has been linked to cognitive decline.

“Consumption of excessive amounts of sugar over a prolonged period is known to affect the health of your heart and excessive sugar may increase blood pressure,” says McDermott. “This can affect brain health if not managed.”

The fix: You don’t have to cut out all forms of sugar altogether. McDermott points out that the brain’s main source of energy is glucose, which we get from eating carbohydrates.

However, scientists recommend trying to get more of your sweet fix from fruits, where the sugar is tied up within fibre and has less of a detrimental impact on your health. They also suggest trying to rewire your brain and taste buds to expect less sweetness by cutting down on consuming added sugars. Such changes can take effect within as little as two weeks, leading to fewer sugar cravings.

5. Social isolation

Humans are inherently social creatures, yet as we get older, our social circle tends to diminish. However, research suggests that more isolated people tend to experience faster brain ageing.

Brennan points to one 2023 study of older adults, which found that those with less frequent social contact had slightly lower total brain volume, including smaller volumes in regions important for memory.

The fix: Neuroscientists say that making time for seeing friends and family, reconnecting with old social contacts and forging new ones becomes increasingly important as we age.

Social interaction is deeply stimulating for our brain, says Brennan. “Even an ordinary conversation requires us to listen, remember, interpret tone and facial expression, predict another person’s response and formulate our own,” she says.

“Regular social contact, therefore, exercises multiple brain networks simultaneously in a way that many solitary activities do not.”

6. Ignoring hearing loss

Few people want to wear a hearing aid or protective earbuds, but the link between protecting your ears and avoiding dementia is becoming increasingly strong.

“People with hearing loss consistently show reductions in overall cognitive function and brain processing speed,” says Lawlor.

One possible explanation, he says, is that as hearing deteriorates, the brain has to work harder to decode sound and so has fewer resources left for memory and thinking. At the same time, hearing loss can have social consequences — conversations require more effort, and so people tend to withdraw, with the resulting loneliness having even more detrimental effects on their brain health.

The fix: Don’t be afraid of taking steps to protect your hearing, such as wearing earbuds at concerts, or getting your hearing tested and starting to wear a hearing aid at the first sign of decline.

“The use of hearing aids may reduce the risk of cognitive decline and dementia,” says Lawlor.