"Do a sudoku a day to keep your brain young" is one of the most repeated claims about the puzzle. It sounds plausible: sudoku asks you to hold several possibilities in mind, check rows, columns and boxes, and reason step by step without guessing. But "sounds plausible" is not the same as "has been shown". In this article we look at what the research actually found, how strong that evidence is, and how to get real value from the time you spend on a grid. No miracle promises, just the studies and what they can and cannot tell us.
What the studies found
Very little research has tested sudoku on its own. Most of the evidence comes from three kinds of studies: large observational surveys of people who already do puzzles, long-term studies of "intellectual engagement" in general, and randomised trials of structured cognitive training. Each answers a different question, so it helps to look at them one by one.
PROTECT: puzzle fans score higher (Brooker et al., 2019)
The study most often quoted in sudoku headlines comes from the UK PROTECT online cohort. Researchers from the University of Exeter and King's College London analysed 19,078 healthy volunteers aged 50 to 93. Participants reported how often they did number puzzles such as sudoku, and completed online cognitive tests covering reasoning, attention, information processing, executive function, working memory and episodic memory.
The result was striking: puzzle frequency was associated with performance on all 14 cognitive measures. People who said they did number puzzles more than once a day scored better than all other groups on 10 core measures, although not every one of those differences was statistically significant.
Limitation: this is a cross-sectional, correlational study. It shows that puzzle use and test scores go together at one point in time, not that puzzles caused the higher scores. The participants were self-selected online volunteers, and puzzle frequency was self-reported. The authors themselves say further research is needed on the type and difficulty of puzzles before the findings can be treated as a potential intervention. Alzheimer's Society, which helped fund the study, put it plainly:
"Unfortunately it doesn't yet mean that regular games of Sudoku or jigsaw puzzles will definitely prevent dementia." (Alzheimer's Society, 2019)
"Use it or lose it"? A 15-year follow-up (Staff et al., 2018)
If puzzlers score higher, is it because puzzles protect the brain, or because sharper people enjoy puzzles? A study in the BMJ tackled exactly this. It followed 498 people born in 1936 in north-east Scotland, whose cognitive ability had been tested at age 11 in the Scottish Mental Survey of 1947, and measured their memory and processing speed repeatedly over about 15 years in later life.
People who reported more intellectual engagement, especially problem-solving activities, had higher cognitive scores in later life. But engagement did not change the rate of age-related decline. Engagement was also correlated with childhood ability and education. The authors' interpretation: mentally active people tend to start ageing from a higher level, rather than declining more slowly.
Limitation: it is observational, a single birth cohort, and engagement was measured by questionnaire. It does not rule out small benefits, but it is a useful warning against reading too much into studies like PROTECT.
Crosswords versus brain games in mild cognitive impairment (Devanand et al., 2022)
One of the few randomised trials involving a classic puzzle was published in NEJM Evidence. 107 people with mild cognitive impairment were randomly assigned to 12 weeks of intensive home-based training with either web-based crossword puzzles or computerised cognitive games, followed by booster sessions, and were followed for 78 weeks.
On the main cognitive scale, the crossword group did slightly better than the games group, and the difference was statistically significant. The crossword group also did better on one measure of everyday functioning.
Limitation: the trial was small, it studied crosswords rather than sudoku, and it compared two active activities without a "do nothing" control group. So it suggests crosswords were not worse than commercial brain games, and possibly better, but it cannot tell us how much either helps compared with no puzzles at all.
The ACTIVE trial: training can last, but stays specific (Rebok et al., 2014)
ACTIVE is one of the largest randomised trials of cognitive training ever run. It enrolled 2,832 independently living older adults (average age 73.6) in six US cities. Groups received ten sessions of training in memory, reasoning or speed of processing, with booster sessions later, and were compared with a no-contact control group. Note that this was structured training, not sudoku.
Ten years later, reasoning and speed-of-processing training still showed effects on the specific abilities that had been trained; memory training no longer did. All three trained groups reported less difficulty with everyday tasks such as managing finances or medication, and about 60% of trained participants versus 50% of controls were at or above their baseline level on that self-reported measure.
Limitation: the everyday benefits were self-reported, the effects were strongest for the skills directly trained, and we cannot assume that sudoku would produce the same results as these specific programmes.
The big skeptical review (Simons et al., 2016)
A team of psychologists reviewed the published studies that leading brain-training companies cited as evidence for their products. Their conclusion is the most important idea for anyone who hopes a puzzle will make them "smarter in general". They found extensive evidence that people get better at the tasks they practise, less evidence for closely related tasks, and
"little evidence that training enhances performance on distantly related tasks or that training improves everyday cognitive performance." (Simons et al., 2016)
They also found that many studies had serious design weaknesses. Applied to sudoku, this means the most reliable effect of solving many sudokus is that you become better at sudoku.
The bigger picture: the Lancet Commission (2024)
The 2024 report of the Lancet Commission on dementia prevention identified 14 modifiable risk factors, including less education, hearing loss, high LDL cholesterol, depression, head injury, physical inactivity, diabetes, smoking, high blood pressure, obesity, excessive alcohol, social isolation, air pollution and untreated vision loss. Together they are estimated to account for around 45% of dementia cases worldwide, which in principle could be delayed or reduced. "Not doing puzzles" is not on that list. That does not make puzzles useless, but it shows where the strongest evidence for brain health currently lies.
What this means: myths and reality
| Common claim | What the evidence supports |
|---|---|
| "Sudoku prevents Alzheimer's." | No study has shown this. Associations exist, but they do not prove cause and effect. |
| "Puzzle lovers have sharper brains." | Often true on average, but people who enjoy puzzles may differ in education, lifelong ability, health and lifestyle. |
| "Sudoku trains your memory for everyday life." | Transfer from one task to everyday cognition is debated and generally weak. |
| "Puzzles are pointless." | Also wrong. Sudoku is a genuine exercise in logic and focus, it is enjoyable, and enjoyment helps people stay mentally engaged. |
The honest summary: sudoku is a good, low-cost mental activity and a pleasant habit, but it is not a medical treatment. The more convincing reasons to play are the ones you notice directly: a calm period of concentration, the satisfaction of a clean deduction, and the slow improvement that comes from learning new techniques. If you are worried about your memory, talk to a doctor rather than relying on puzzles.
How to get real value from sudoku
Since the research suggests that benefits are tied to how you practise, here are some realistic ways to make your puzzle time more rewarding.
- Learn techniques instead of repeating easy grids. Solving dozens of puzzles at the same level mostly rehearses the same moves. Start with the basics in our guide to naked singles and hidden singles, then move on to more advanced patterns.
- Stay in the "slightly too hard" zone. Choose a level where you have to think, but can still finish. When a level feels automatic, step up in our sudoku game.
- Use notes on purpose. Pencil marks are not cheating. Writing candidates and eliminating them systematically is exactly the kind of structured reasoning the puzzle rewards.
- Avoid guessing and hints. Try to justify every number with a reason. If you get stuck, look for one more deduction before reaching for a hint.
- Time-box it. 15 to 20 focused minutes is enough for a satisfying session. A fixed routine such as the daily sudoku makes the habit easy to keep without it taking over your evening.
- Review your mistakes. When a grid goes wrong, find the step where the logic failed. That reflection is where most learning happens.
- Mix it up. Because transfer is limited, variety matters: learn a language, play an instrument, read, try other logic puzzles.
- Combine with what has stronger evidence. Regular physical activity, good sleep, social contact, and looking after hearing, blood pressure and general health are what mainstream guidance emphasises. Solving with a friend or a grandchild combines two of those at once.
Conclusion
Does sudoku keep your brain sharp? The fair answer is: people who do puzzles tend to perform better on cognitive tests, but the research so far cannot show that puzzles are the reason, and benefits beyond the puzzle itself appear to be modest at best. That is not a reason to stop. Play sudoku because you enjoy it, use it to learn and to focus, and treat it as one part of a broader healthy routine rather than a shortcut to a younger brain.
Sources
- Brooker H, Wesnes KA, Ballard C, Hampshire A, Aarsland D, Khan Z, Stenton R, Megalogeni M, Corbett A. The relationship between the frequency of number-puzzle use and baseline cognitive function in a large online sample of adults aged 50 and over. International Journal of Geriatric Psychiatry. 2019;34(7):932–940. doi:10.1002/gps.5085 · PubMed 30746778
- Staff RT, Hogan MJ, Williams DS, Whalley LJ. Intellectual engagement and cognitive ability in later life (the "use it or lose it" conjecture): longitudinal, prospective study. BMJ. 2018;363:k4925. doi:10.1136/bmj.k4925 · PubMed 30530522
- Devanand DP, Goldberg TE, Qian M, et al. Computerized games versus crosswords training in mild cognitive impairment. NEJM Evidence. 2022;1(12). doi:10.1056/EVIDoa2200121 · PubMed 37635843
- Rebok GW, Ball K, Guey LT, et al.; ACTIVE Study Group. Ten-year effects of the Advanced Cognitive Training for Independent and Vital Elderly cognitive training trial on cognition and everyday functioning in older adults. Journal of the American Geriatrics Society. 2014;62(1):16–24. doi:10.1111/jgs.12607 · PubMed 24417410
- Simons DJ, Boot WR, Charness N, Gathercole SE, Chabris CF, Hambrick DZ, Stine-Morrow EAL. Do "brain-training" programs work? Psychological Science in the Public Interest. 2016;17(3):103–186. doi:10.1177/1529100616661983 · PubMed 27697851
- Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet. 2024;404(10452):572–628. doi:10.1016/S0140-6736(24)01296-0 · PubMed 39096926
- Alzheimer's Society. Word and number puzzles improve adult cognitive function (news statement, 16 May 2019). alzheimers.org.uk