Studies Show Exercise Reduces Dementia Risk

A daily, half-hour of brisk walking has significant impact

July 22, 2011A new study finds a strong relationship between activity energy expenditure and the risk of cognitive impairment.

Evidence continues to mount that physical exercise reduces a person’s risk of dementia.

In some of the latest research, scientists measure actual physical activity, rather than rely on people's imperfect memories.

Most researchers studying physical activity and dementia rely on self-reporting. So they'll ask people in a study about what exercise they've had in the past week, for example.

But there are problems with self-reporting. Laura Middleton of the Sunnybrook Research Institute and the University of Waterloo in Canada says for one thing, people just don't remember what they've done. Also, people tend to report certain types of activities more than others.

"[Self-reporting] does a very good job of capturing jogging or biking or tennis, but does a relatively poor job of capturing low-intensity activity like walking or daily chores, which may also be important to the risk of cognitive impairment."

To get around that problem, Middleton measured physical activity with an established technique that uses doubly labeled water, made from isotope variants of hydrogen and oxygen. Participants in the five-year study drank a small amount of this special water, and by measuring the isotope variants in their urine, their energy expenditure can be calculated.