Sustained activity seems to lower the risk of Alzheimer's disease and certain other neurological disorders, according to researchers in the United States and Germany.

"Our study suggests that, in mice, we can reduce the effects of aging on the brain with a sustained active and challenging life, even if this stimulation is only begun in middle age," said the study's lead author, Dr. Gerd Kemperman.

The study linked two distinct lines of research. One focused on people who are active in their middle to later years, whether physically or intellectually, where researchers have found they are less susceptible to cognitive decline or diseases such as Alzheimer's.

Another focuseds on the hippocampus -- a structure in the brain critical to normal cognitive function and storing new memories. It is one of few areas in the brain that generates new nerve cells in adults.

In order to determine if the regeneration of nerve cells could be sustained long-term in middle and later life, and if there were corresponding effects on mental abilities, researchers followed two groups of mice for 10 months.

The mice, aged 10 to 20 months (middle-to-old age in rodent years), were housed in either a small bare cage with a few other mice, or in an enhanced environment, which included a large cage with running wheel, plastic tunnels and other objects, shared with many mice.

The enhanced environment was rearranged from time to time as well.

Reporting in the Annals of Neurology, researchers found that mice living in enriched surroundings were generating five times as many nerve cells as the mice in the bare environment, showing that "activity can have a sustained effect, even on older animals."

Additionally, the same mice also fared significantly better on behavioral tests. They were able to explore -- and adapt to -- new environments quicker, and outperformed the other mice in standard learning tests.

Kemperman said he is hopeful that the results will prove relevant for humans as well.

"Activity will certainly do no harm and most likely benefit people if they use our results as a motivation to be more active," he said. "They might even do something good for the nerve cells that are involved in learning and memory processes."

Other Sources: Annals of Neurology