WASHINGTON: Devoting half an hour to aerobic exercises several times a week may help prevent memory loss in old age, say neurologists at Yale University.

A study conducted on mice suggests that keeping the brain healthy and active reduces the chances of memory decline in old age.

"It is important for people of all ages to do 20 to 30 minutes of aerobic exercise several times a week. Keeping a healthy and active brain may prevent memory decline in old age, but only a longitudinal study that follows mice over time could confirm this possibility," says Dr. Daryn Frick, author of the study published in the journal Behavioral Neuroscience .

The researchers assigned 160 female mice who were young, middle-aged and old adults (about 3, 15, or 21 months old) to either an experimental (treatment) condition or a control group. Treatment conditions included cages where mice could exercise on running wheels, cages where they could play with toys, or cages with both for complex enrichment. The control mice cages were unadorned.

Among all mice, spatial memory had worsened with age.

Upon testing the animals' ability to navigate a spatial water maze after the initial four weeks of treatment, the researchers found that exercise alone significantly improved the spatial memory of the young mice.

Both exercise alone and complex enrichment, but not cognitive stimulation alone, significantly improved memory among the middle aged, say researchers. For old mice, all enrichments (alone or combined) significantly improved performance.

The study's authors note that as people get old and maybe less able to exercise, cognitive stimulation can help to compensate.

"These data may suggest that enrichment initiated at any age can significantly improve memory function. And exercise plus mental challenge in middle age - when many people start to notice subtle memory changes - may offer the strongest, most widespread benefits for memory function," write the authors.