FOR TRUE cruciverbalists, little beats the sheer pleasure of filling in that final clue. They should also derive satisfaction from knowing that their addiction affords them substantial protection against Alzheimer’s disease, one of the commonest causes of dementia.

Any intellectually stimulating activity can potentially stave off brain disease but crosswords are particularly well suited to maintaining mental agility — to complete them requires daily, sustained bursts of cognitive effort. The activity features almost universally in checklists of how to ward off neural decline, and is even a component of an experimental “brain boot camp” developed by experts on ageing at the University of California.

One study in this area looked at a group of about 800 Catholic clergy in Illinois. Those who flexed their brains most regularly almost halved their risk of developing Alzheimer’s disease. Another study, conducted by Professor Joe Verghese at Yeshiva University in New York, looked at the leisure pursuits of more than 400 pensioners. While physical exercise did not seem to delay the onset of Alzheimer’s, intellectual exercise did. Those who did four crossword puzzles a week were less likely to develop the disease than those who managed only one.

Other protective activities included chess, draughts, card and board games, museum visits, reading, playing a musical instrument and ballroom dancing (the last two require a good working memory and a degree of co-ordination).

Those who danced regularly displayed the lowest risk. Separate studies have found that being bilingual also helps to preserve brain function.

Such results have given rise to the “use it or lose it” school of thought regarding neurodegenerative diseases. It is unclear, though, how regular brain workouts are able to postpone Alzheimer’s; this is now the subject of ongoing research.

The absence of an obvious biological mechanism has inspired worries that the link between mental exercise and delayed Alzheimer’s onset is fictitious. After all, lovers of crosswords and other puzzles tend to be better educated than the general population.

However, when the data are corrected for such factors, the link persists. This means that even among people who left education early, the ones who enjoy puzzles, play games and stay mentally active still enjoy a lower risk of Alzheimer’s. This strengthens the theory that using your brain regularly really does sharpen and protect it.

Scientists also stress that keeping physically fit — eating well, exercising, not smoking — can help to prevent vascular dementia (induced by strokes), another major cause of age-related neural decline.