Boston, June 19 (Reuters): Want to ward off Alzheimer’s disease? Play some mental games or go dancing.

Elderly people who frequently read, do crossword puzzles, practise a musical instrument or play board games cut their risk of Alzheimer’s and other forms of dementia by nearly two-thirds compared to people who seldom do such activities, researchers said yesterday.

The findings, which stem from a long-term study of people over 75, are the latest to buttress the “use it or lose it” theory of staying mentally sharp.

Previous attempts to test the theory met with controversy because researchers had no way to tell if people who avoided mentally challenging activities were doing so because they were already in the early stages of Alzheimer’s.

But neurologist Joe Verghese and his colleagues at the Albert Einstein College of Medicine in the Bronx, New York, adjusted for that potential complication by following hundreds of elderly volunteers for more than 20 years.

The study, published in today’s New England Journal of Medicine, showed, for example, that volunteers who did crossword puzzles four days a week had a risk of dementia that was nearly half that of subjects who did puzzles once a week.

With the exception of dancing, physical activity did not decrease the risk. Among the 25 people who danced frequently, their chance of developing dementia was 76 per cent lower.

The Verghese team said mentally challenging activities may directly slow down the processes that lead to dementia or, alternatively, create a larger reserve of brain cells that a patient can tap once deterioration begins.

The study did not look at how many hours a day the volunteers performed mental activities, nor at how taxing those activities were on the brain. “Although we didn’t analyse the intensity of the activity, I think that would influence your risk of dementia,” Verghese said. “And I would think an activity that is more challenging would probably be better than something that is less challenging,” he added.

More research is needed to confirm the findings and better understand the influence that genetic, physical activity and mental challenges play in controlling the timing of Alzheimer’s, Harvard’s Joseph Coyle said in a commentary in the Journal.

In the meantime, he encouraged elderly people to read, play board games and go ballroom dancing.