If physical exercise keeps the body young and healthy, does mental exercise do the same for the brain? Does a sudoku a day keep dementia away?

Dr Fred Kavalier answers your health question:

Physical exercise undoubtedly prolongs life and reduces the risk of many diseases, including heart disease, cancer and osteoporosis. There is even some evidence that regular physical exercise reduces the risk of developing dementia. But it is less clear that mental exercises will do the same for the brain. According to the Alzheimer's Society, certain activities are linked to a reduced risk of dementia. These include seeing friends, going to church, playing cards, dancing, travelling, doing odd jobs, knitting, and doing crosswords. It has even been suggested that watching plenty of television will reduce your risk of dementia. But other studies have shown exactly the opposite - that watching too much TV increases the risk.

As for mental exercises, such as maths puzzles and games like Scrabble and sudoku, although there has been a lot of research to try to answer this question, the scientific jury is still out. Most experts believe that mental exercise keeps the brain fit, but they don't yet have the research to prove it.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.