Puzzles such as crosswords and sudoku do not counteract mental decline in old age but can provide a higher point from which decline begins, a study has found.

Researchers found that, while regular problem-solving will boost mental ability in old age, it had no impact on the rate of mental decline associated with ageing.

A team from Aberdeen University and Aberdeen Royal Infirmary said that intellectual activity provided a “higher cognitive point” from which to decline.

Previous studies have suggested that doing puzzles, reading from an early age, playing board games and playing a musical instrument at least twice a week is linked with a reduced risk of dementia.

But the new study said there had been a lack of historical childhood mental ability data and the effect of practice on improving test scores has often been overlooked in mental ageing studies.

The new study, published in the BMJ on Monday, investigated the link between intellectual engagement and mental ability in later life based on 498 people born in 1936.

Researchers used data from the archives of the Scottish Council for Research in Education (SCRE) which had maintained population-based records of the Scottish Mental Surveys of 1947.

All the respondents had taken a group intelligence test called the Moray House Test at the age of 11 and took part in memory and mental processing speed testing up to five times over a 15-year period.

Each person’s education history and National Adult Reading Test Score (NART) were recorded at the start of the study.

Researchers from Aberdeen University and Aberdeen Royal Infirmary also tested their current mental ability using a matching symbols with digits test and a verbal memory test.

They used a version of the typical intellectual engagement (TIE) questionnaire to test levels of existing interest in reading and problem solving, consideration of ideas and intellectual curiosity.

The team found that, despite intellectual activity boosting mental ability in old age, it had no effect on the rate of mental decline caused by ageing.

But the researchers stressed it was an observational study, and it is “impossible for a causal effect to be inferred” because of other unmeasured factors, such as personality.

Dr Roger Staff, honorary lecturer at the Aberdeen University and head of medical physics at Aberdeen Royal Infirmary, said that, although puzzles could enhance mental ability, they do not protect against decline.

He said that “personality may govern how much effort older people put into such activities and why”.