A little bit of exercise helps people improve their memory and brain function, according to a new study.

A team at the University of Melbourne studied 138 people 50 years or older who were considered at risk for dementia from Alzheimer's disease because they were already reporting memory problems.

They were randomly broken into two groups; one got education about the condition and typical care, and the other got a six-month program of three 50-minute workouts -- including walking -- a week.

Using a standard test of cognition used with Alzheimer's patients, researchers found that those in the exercise group had better scores. They also performed better on a dementia rating scale.

Researchers said that the gains were small, but so was the amount of activity. Also, they said that delaying the onset of dementia by just a year per patient would mean 9.2 million fewer cases worldwide.

"Unlike medication, which was found to have no significant effect on mild cognitive impairment at 36 months, physical activity has the advantage of health benefits that are not confined to cognitive function alone, as suggested by findings on depression, quality of life, falls, cardiovascular function and disability," they wrote.