Lowering the risk of cognitive decline

Can exercise reduce the risk of dementia?

Regular activity is linked with a lower risk of dementia, but nobody can promise that exercise will prevent it. Among middle-aged and older adults, people who were regularly active had about 25% lower risk of dementia, although results varied a lot from group to group¹.

That link isn't proof. Activity tends to fall in the years before a dementia diagnosis⁴, so being less active can be an early sign of brain changes rather than the cause. Much of the evidence covers short periods, which makes this mix-up more likely³. Trials of aerobic exercise on its own in healthy older adults found no thinking benefit⁵.

International guidance takes a careful middle path. For people with no sign of dementia or mild memory and thinking problems, activity may be considered for preventing dementia. Experts agreed it may delay onset, but the evidence is uncertain and activity should be part of a broader approach². It shouldn't be presented as an established or fully proven way to prevent dementia⁶.

A common target is at least 150 minutes of moderate activity a week, or at least 75 minutes of vigorous activity, or a mix of the two⁷. Every bit of activity counts, so start with what you can manage and build up gradually.

What does the evidence say about activity and cognitive decline?

The evidence is mixed, and the fairest reading is that activity may help the brain a little. Large reviews find only a very small link between being active and slower decline in thinking, with no clear pattern between how much people do and how well they think. The link is not seen in studies that followed people for more than 10 years³. Still, even a small effect can matter across a whole population if people stay active for decades³.

Exercise programmes for adults over 50 have been linked with better thinking, particularly sessions of 45–60 minutes at moderate intensity or above. The suggestion is a mix of aerobic and strength training, on as many days of the week as possible⁸. Treat that as a direction, not a rule: no clear minimum amount for the brain has been shown, so build up gradually.

Results from trials point both ways. Thinking scores improved just as much with stretching as with aerobic exercise in sedentary older adults, so the gain can't be put down to aerobic exercise alone⁹. Exercise as a single change gave inconclusive results, though a small benefit was suggested¹⁰.

Sessions that combine walking or other aerobic activity with some strength work are one sensible option.

How does lifelong activity build brain reserve?

Brain reserve (also called cognitive reserve) is the idea that a brain can keep working well despite ageing or damage. It is a hypothesis: activity is thought to help, but that isn't proven. Reserve is described as a capacity that lets the brain cope with disease or injury without clear symptoms¹¹. Education, the complexity of your work and leisure activities are the usual stand-in measures for it¹², so leisure activity is a marker here, not a tested treatment.

Reserve seems to build up across life rather than being fixed in childhood¹³. Physical activity is described as protecting brain structure and size, while mentally stimulating activity strengthens how brain circuits work, so each may support reserve in a different way¹⁴. People who were more active tended to keep better thinking even when their brains showed similar damage, which suggests activity may help people hold on to their abilities¹⁵. How lifestyle builds reserve is still unclear, though¹⁵.

For you, this means a lifetime of activity isn't a requirement. Lifelong exercise may be preferable, but starting at any age to delay cognitive decline is worthwhile⁸. If you haven't been active before, you haven't missed your chance.

How does lifelong activity protect the ageing brain?

There are several ideas about how regular activity might protect the brain, and none is proven. Guidance lists more blood flow to the brain, higher levels of nerve-growth factors such as BDNF, less inflammation, and better control of conditions such as high blood pressure and diabetes¹⁶. Higher activity is also linked with less cardiovascular disease, a common risk factor for dementia². So looking after your heart and blood vessels may be part of the story. That heart-to-brain link is a hypothesis; the heart benefits themselves are well established.

Brain scans offer a small clue. Aerobic exercise has been linked with a modest increase in the size of the hippocampus, a memory-related region^2,7. Yet in sedentary older adults, aerobic exercise and stretching both improved thinking, and neither prevented the loss of brain volume that comes with age⁹.

Activity also lowers the risk of falls⁷. Falls are a common cause of head injury, which has been linked with a higher risk of cognitive decline and dementia⁷. Take care with footing and surroundings as you build up activity.

Can new and varied activities keep an ageing brain healthy?

Learning something demanding and new seems to help memory, while variety on its own hasn't been shown to. Learning a demanding new skill improved episodic memory (remembering events and experiences) more than easier, passive activities did in older adults. Socialising, swapping information and novelty alone showed no thinking benefit, though more work is needed before the social finding is seen as definitive¹⁷.

Physical activity has firmer support. In adults over 50, aerobic, resistance, multicomponent and tai chi programmes each showed benefit, though the tai chi evidence rests on few studies and needs confirming⁸. Only a small amount of strength work seems needed to show benefits for memory¹⁸. Which type works best, and for whom, is still unclear¹⁸.

Exercise programmes that include mental tasks, such as multitasking or memory exercises, improve thinking in older adults¹⁰. Programmes that combine several lifestyle changes including exercise have given mixed results on cognitive decline⁷.

When to check with a health professional

If you're starting exercise after a long break, it's always a good idea to see your doctor first.

A WHO guideline considers physical activity safe for adults living with chronic conditions such as hypertension or type 2 diabetes, and says the benefits generally outweigh the risks¹⁹. For an injury or a health condition, see a health professional, such as your doctor or a physio.

Build up gradually. If a muscle or joint is sore, or soreness appears a day or two later, ease off, and see a doctor or other health professional if it persists or gets worse. Don't push through feeling sick, sweaty or unwell, unexplained discomfort, or breathlessness or dizziness that doesn't settle. If it is mild and passing, see a doctor.

Call your local emergency number for chest pain or pressure (or pain spreading to the arm, neck, jaw or back, especially with sweating or feeling sick), severe breathlessness, fainting or collapse, signs of a stroke, a serious injury, or someone who isn't safe.

If memory problems persist or affect daily life, see a doctor rather than assuming it's normal forgetfulness or trying to work it out yourself. Exercise doesn't replace any medical care or treatment you've been given.