Doing crossword puzzles, reading, and playing cards daily may delay the rapid memory decline that occurs if people develop dementia, according to a U.S. study.

Researchers from New York's Albert Einstein College of Medicine spent five years following 488 people aged 75 to 85 who did not have dementia at the start of the study.

During the study period, 101 of these people developed dementia.

At the start of the study the participants reported how often they participated in six leisure mind activities - reading, writing, doing crossword puzzles, playing board or card games, having group discussions, and playing music.

For each activity, daily participation was rated at seven points, several days a week was rated at four points, and weekly participation was rated at one point.

The average score for those who later developed dementia was seven points, meaning they took part in one of the six activities each day on average.

Ten people reported no activities, and 11 reported only one activity per week.

The researchers then looked at the point when memory loss started accelerating rapidly and found that for every additional activity a person participated in, the onset of rapid memory loss was delayed by 0.18 years.

"The point of accelerated decline was delayed by 1.29 years for the person who participated in 11 activities per week compared to the person who participated in only four activities per week," said researcher Charles Hall in a statement.

He said that the results remained valid after researchers factored in the education level of the participants.

"These activities might help maintain brain vitality. Further studies are needed to determine if increasing participation in these activities could prevent or delay dementia," said Hall.

The study, published in the journal Neurology, was supported by the National Institute on Aging.