The 2024 Lancet Commission on dementia estimates that about 45% of future dementia could, in theory, be prevented or delayed by tackling 14 risk factors, and most of them are things you control in your 40s and 50s. Exercise is one of the few habits that touches several of them at once. The best evidence points to a mix of aerobic and strength training, at least moderate intensity, in sessions of around 45 minutes, on as many days as you can manage.
Here is what that means for a busy man with three or four hours a week to train.
Key takeaways
- The Lancet Commission lists 14 modifiable dementia risk factors. Physical inactivity is one, and exercise also improves several others, including blood pressure, diabetes, weight and low mood.
- A 36-study meta-analysis in adults over 50 found exercise improved cognitive function, with aerobic, resistance, multicomponent training and tai chi all showing benefits.
- The clearest gains came from sessions of 45–60 minutes at moderate or vigorous intensity.
- A single workout gives a small, short-lived lift in some aspects of thinking on the day you do it.
- Midlife is the window that matters. The Commission’s advice is to lower risk early and keep it low for as long as possible.
Why your brain cares about what you do at 40
Dementia feels like a problem for your parents’ generation, not yours. The numbers say otherwise. The World Health Organization reports that 57 million people were living with dementia worldwide in 2021, with nearly 10 million new cases every year. It is currently the fifth leading cause of death globally.
The diseases behind dementia develop slowly, over decades. That is why the Lancet Commission’s 2024 update focuses so heavily on midlife. Its headline message is to reduce risk factors early, “the earlier, the better”, and keep them low throughout life.
In its 2020 report the Commission counted 12 risk factors and put the preventable share at about 40%. The UK’s NHS still quotes that “around 4 in 10” figure. The 2024 update added two more factors, high LDL cholesterol in midlife and untreated vision loss, raising the estimate to roughly 45%.
Two caveats keep this honest. First, “potentially preventable” is a population estimate, not a promise for any one person. Genes, age and luck still matter. Second, most of the evidence linking exercise to dementia comes from observational studies, which show associations rather than proof of cause. The trials on thinking skills, covered below, are stronger evidence that training helps your brain work better.
The 2-minute brain risk self-check
Go through the 14 factors below and tick the ones that apply to you right now. This is not a diagnostic test. It is a quick way to see where your effort will count most, and how many of the factors your training can reach.
| Risk factor | Quick check | Does exercise help? |
|---|---|---|
| Physical inactivity | Under 150 minutes of moderate activity a week? | Yes, directly |
| High blood pressure | Not measured in the last year, or above target? | Yes, it lowers blood pressure |
| Type 2 diabetes | Raised blood sugar or HbA1c? | Yes, it improves insulin sensitivity |
| Obesity | Waist growing, or BMI in the obese range? | Partly, alongside diet |
| High LDL cholesterol | No lipid test in the last few years? | A little; diet and sometimes medication matter more |
| Depression | Low mood or loss of interest for weeks? | Yes, as a support to proper care |
| Social isolation | Rarely see friends outside work and family? | Yes, if you train with others |
| Excess alcohol | More than 14 UK units (about 112 g of alcohol) a week? | Indirectly |
| Smoking | Any cigarettes? | Indirectly; stopping is the step |
| Hearing loss | Struggling to follow conversations in noisy places? | No; get a hearing test |
| Untreated vision loss | No eye test in two years? | No; get an eye test |
| Traumatic brain injury | Cycling without a helmet, or repeated head knocks in sport? | Train smart and protect your head |
| Air pollution | Running or cycling along busy roads? | Choose parks and quieter routes |
| Less education | Stopped learning new skills? | Learning a new sport or skill counts as mental challenge |
How to read it: count your ticks, then look at the right-hand column. For most men, at least half of the ticks sit in rows where regular training makes a real difference. The others, such as hearing, eyesight and cholesterol, usually need a quick appointment rather than willpower.
The Commission’s figures put high midlife LDL cholesterol at about 7% of potentially preventable dementia, one of the largest single shares. If you have never had a lipid test, it is worth booking one. Our guide to heart health numbers after 35 explains which results to ask for.
What the research shows about exercise and your brain
Training can grow the brain’s memory centre
The hippocampus is a part of the brain central to memory, and it shrinks gradually with age. In a well-known randomised controlled trial of 120 older adults, published in PNAS in 2011, a year of aerobic exercise training increased hippocampal volume by 2%. The authors described this as effectively reversing age-related volume loss by one to two years. Spatial memory improved too.
The control group’s hippocampal volume declined over the same year, but participants with higher fitness at the start lost less. The researchers concluded that fitness appears to protect against volume loss. Those volunteers were older than you, so treat this as a sign of what the brain can do, not a forecast for a 40-year-old.
Exercise improves thinking skills in adults over 50
A 2018 systematic review and meta-analysis in the British Journal of Sports Medicine pooled 36 studies of supervised exercise in adults over 50. Exercise improved cognitive function, with an overall effect size of 0.29, a small to moderate effect. The benefit held regardless of whether participants started with normal thinking or mild impairment.
The details are what make this useful:
- Type: aerobic exercise, resistance training, multicomponent training and tai chi all showed significant benefits. Yoga did not reach significance, but only two yoga studies were included.
- Session length: sessions of 45–60 minutes were linked with benefit. Shorter and longer sessions did not show a significant effect in this analysis.
- Intensity: moderate and vigorous intensity helped. Low intensity did not reach significance.
The authors’ practical conclusion was a programme combining aerobic and resistance training, at least moderate intensity, at least 45 minutes per session, on as many days of the week as possible.
One workout gives a small same-day boost
You do not have to wait months. The US Physical Activity Guidelines state that a single session of moderate-to-vigorous activity can reduce anxiety and improve some aspects of thinking on the day you do it. A 2012 meta-analysis of 79 studies found the effect of a single bout on cognitive performance was positive but small, during exercise, straight after and after a delay. Duration, intensity and fitness all changed the size of the effect.
Small is the honest word here. A lunchtime walk will not turn a bad day into a brilliant one, but it can take the edge off afternoon fog.
Myths vs evidence
| Myth | What the evidence says |
|---|---|
| “Brain health is all genetics.” | Genes matter, but the Lancet Commission estimates about 45% of dementia is linked to 14 modifiable factors. |
| “Only cardio helps the brain.” | In the 2018 meta-analysis, resistance training also improved cognition. Combining both looked best. |
| “Brain games are enough.” | Puzzles and apps challenge the mind, but they do nothing for blood pressure, blood sugar or fitness. Exercise reaches more of the risk factors. |
| “It’s too late to start at 45.” | The trials above recruited people over 50 and older adults, and still found benefits. Starting at 35–50 gives you more time. |
| “Any movement is just as good.” | All activity helps general health, but cognitive gains in the meta-analysis came from at least moderate intensity. |
| “Ten thousand steps protects your brain.” | Walking more is good for you, and our guide to walking vs running covers step targets, but no single step count is proven to protect your brain. |
A brain-friendly training week in 3–4 hours
This plan follows the meta-analysis findings and the NHS advice of 150 minutes of moderate aerobic activity plus strength work on at least two days a week. It fits roughly 3.5 hours.
| Day | Session | Time | Brain angle |
|---|---|---|---|
| Monday | Strength A: squat, row, press, carry | 45 min | Resistance training, blood sugar control |
| Tuesday | Zone 2 cardio: brisk walk, bike or easy jog | 45 min | Aerobic fitness, blood pressure |
| Wednesday | 10-minute walk after lunch or before a big meeting | 10 min | Same-day focus boost |
| Thursday | Strength B plus 4 x 3 min harder intervals | 50 min | Multicomponent, vigorous effort |
| Friday | Rest or mobility | – | Recovery |
| Saturday | Sport or a long walk, ride or hike with friends | 60 min | Social contact, skill learning |
| Sunday | Rest or easy family walk | – | Sleep and recovery |
Getting the intensity right
Moderate intensity means you can talk in full sentences but not sing. Vigorous means you can only say a few words. For most of your aerobic work, aim for that comfortable but purposeful zone 2 effort. Our zone 2 training guide shows how to pace it by heart rate or by feel.
If you are new to lifting, start with the basics in our strength training after 35 plan. Two full-body sessions a week are enough to start.
Make it social and make it new
Social isolation is one of the 14 factors, and learning new skills adds mental challenge. A weekly game of football, padel, tennis or cricket, a running club or a group ride ticks both boxes. If your friendships have thinned out since the kids arrived, our piece on loneliness in midlife men has practical ways back in.
When you only have 20 minutes
The 45-minute finding comes from supervised trials, not a hard rule. Shorter sessions still count towards your 150 weekly minutes and the wider health benefits. On busy weeks, do what you can and keep the habit alive.
The habits outside the gym that protect your brain
- Sleep: poor sleep makes the next day’s thinking worse, and the Physical Activity Guidelines list better sleep among the brain benefits of exercise. Our guide to sleeping better after 35 covers the basics.
- Blood pressure: know your numbers and keep them in a healthy range. The NHS lists this among its main dementia prevention steps.
- Alcohol: the NHS advises no more than 14 units a week for men and women.
- Weight: the NHS says losing even 5% to 10% of excess weight can help reduce dementia risk.
- Hearing and eyesight: book a hearing test if conversations in busy places are hard, and an eye test if yours is overdue.
- Protect your head: wear a helmet on the bike and take head knocks in sport seriously.
- Move during the day: the NHS lists sitting for most of the day as a risk factor and advises getting up and moving regularly.
Safety note: If you have heart disease, high blood pressure, diabetes or chest pain, breathlessness or dizziness on exertion, talk to your doctor before you add vigorous intervals. Memory problems that are new, getting worse or worrying the people around you deserve a proper medical check rather than a training plan. They often have treatable causes, such as low vitamin B12, thyroid problems, sleep apnoea, low mood or medication side effects.
Need to talk to someone now? Low mood and brain fog often travel together. If you are struggling or having thoughts of harming yourself, please reach out today. US and Canada: call or text 988. UK and Ireland: Samaritans on 116 123. Australia: Lifeline on 13 11 14. India: Tele-MANAS on 14416. Colombia: Línea 106. Elsewhere, find a free helpline at findahelpline.com. Our guide to men’s mental health after 35 explains how to get support.
FAQ
What is the best exercise for brain health?
There is no single best one. In the 2018 meta-analysis, aerobic exercise, resistance training, combined programmes and tai chi all improved cognition in adults over 50. A mix of aerobic and strength training at moderate intensity or higher is the best-supported approach.
How much exercise do I need to protect my memory?
The trials that showed cognitive gains used sessions of about 45–60 minutes at moderate or vigorous intensity, on as many days as possible. For general health, the NHS recommends at least 150 minutes of moderate aerobic activity a week plus two strength sessions.
Can exercise prevent dementia?
No habit can guarantee it. Physical inactivity is one of 14 modifiable risk factors, and exercise also improves blood pressure, blood sugar, weight and mood. Together, these factors account for an estimated 45% of dementia in the population, so staying active is a sensible part of lowering your risk.
Does exercise help brain fog?
It can give a small lift on the day you train, and better fitness and sleep help over time. If brain fog is persistent, see your doctor, because causes such as poor sleep, low mood, thyroid problems or low B12 need checking.
Is it too late to start at 45 or 50?
No. The trials that found benefits recruited adults over 50 and older adults. Starting in your 40s gives you more years of benefit and more time to bring other risk factors down.
Free tool: test how fast your brain and hands work together with the reaction time test, then see how today’s habits could shape your next decades with Future You.
Sources
- Livingston G, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet, 2024.
- Alzheimer Europe. 2024 Lancet Commission underscores potential for dementia risk reduction, identifying 14 modifiable risk factors.
- World Health Organization. Dementia fact sheet.
- Erickson KI, et al. Exercise training increases size of hippocampus and improves memory. PNAS, 2011.
- Northey JM, et al. Exercise interventions for cognitive function in adults older than 50: a systematic review with meta-analysis. Br J Sports Med, 2018.
- Chang YK, et al. The effects of acute exercise on cognitive performance: a meta-analysis. Brain Research, 2012.
- US Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition, 2018.
- NHS. Can dementia be prevented?
This article is for general education and is not medical advice. Check with your doctor before starting a new training or nutrition plan, especially if you have a health condition.
