Use it or lose it. That pretty well sums up the conclusion of an important study released a few days ago in the prestigious New England Journal of Medicine. The study, which looked at whether increased participation in leisure activities lowers the risk of Alzheimer's disease and dementia, found that people who did crossword puzzles (or who read, wrote for pleasure, enjoyed board games or played cards or musical instruments) experienced Alzheimer's and dementia less than those who did not.

The study is an important one, experts say. Because the incidence of dementia increases with age and because we are an aging society, the issue is emerging as a major public health priority.

But little has been studied as to how to protect against dementia. Aging baby boomers are concerned with this topic, says Boston's Dr. Joseph Coyle, a professor of psychiatry and neuroscience at the Harvard Medical School. Though Coyle was not involved in the study, he wrote the commentary on it for the medical journal: "This study is actually one of a large series of studies carried out that indicate that being involved in mentally challenging activities and having extensive social networks is protective not only against dementia, but also death," says Coyle.

The community-based study followed 469 subjects older than 75 years of age for more than five years. All were free of Parkinson's disease, liver disease, alcoholism or any known terminal illness.

They were interviewed often as to their participation in six cognitive activities (including reading, doing crossword puzzles and playing cards) and 11 physical activities (from tennis to golf to dancing). Dancing was the only physical activity associated with a lower risk of dementia.

The study's findings do not surprise Corey Mackenzie, a psychologist at Toronto's Baycrest Geriatric Centre. "Existing research already shows how participation in a variety of leisure activities is associated with better memory performance and a lower risk of dementia," he says. "In general, more is better in that people who are engaged in a number of interesting hobbies or challenging activities are better off than people who don't do these things."

Mackenzie tells his clients the key is to find something you like to do: "Memorizing words out of a dictionary is not going to be useful. There has to be an element of enjoyment to it, of being actively challenged."

In the memory and aging program he runs, he teaches people how memory changes with age and how to keep that memory tuned: Call (416) 785-2500, ext. 2445, to find out more about the $90 five-week program.

Mackenzie says that staying mentally active may actually change the brain cell structure: Experiments have shown that rats that live in stimulating environments have increased connections between their brain cells compared to bored rats.

According to Coyne, the activities referred to in the study may generate stem cells in the brain to work around the toxic effects of amyloid, which appears to be responsible for Alzheimer's. "If you're at risk, and most of us are if we live long enough, these types of activities may put off that risk for a significant amount of time."

While the list of activities mentioned in this study is not exhaustive, other studies around the world have shown that even knitting, gardening or travelling reduced the risk of dementia. Coyne says that while games like bingo and canasta have not been studied, a simple bingo game requires concentration and attention to detail: "I would see that as a mentally challenging task and it also reinforces social networks."

And keep up those crossword puzzles. Elderly people who did crosswords four days a week had a 47-per-cent lower risk of dementia than those who did puzzles once a week.