WASHINGTON — Mastering a second language can pump up your brain in ways that seem to delay getting Al zheimer's disease later on, scientists said Friday.

Never learned to habla or parlez? While the new research focuses mostly on the truly long-term bilingual, scientists say even people who tackle a new language later in life stand to gain.

The more proficient you become, the better, but "every little bit helps," said Ellen Bialystok, a psychology professor at York University in Toronto.

Much of the study of bilingualism has centered on babies, as scientists wondered why simply speaking to infants in two languages allows them to learn both in the time it takes most babies to learn one.

Their brains seem to become more flexible, better able to multitask. As they grow up, their brains show better "executive control," a system key to higher functioning — as Bialystok puts it, "the most important part of your mind."

But does that mental juggling while you're young translate into protection against cognitive decline when you're old?

Bialystok studied 450 Alzheimer's patients, all of whom showed the same degree of impairment at the time of diagnosis. Half are bilingual, having spoken two languages regularly for most of their lives. The rest are monolingual.

The bilingual patients had Alzheimer's symptoms and were diagnosed between four and five years later than the patients who spoke only one language, she told the annual meeting of the American Association for the Advancement of Science.

Being bilingual does nothing to prevent Alzheimer's disease from striking. But once the disease does begin its silent attack, those years of robust executive control provide a buffer so that symptoms don't become apparent as quickly, Bialystok said.

What is it about being bilingual that enhances that all-important executive control system? Both languages are essentially turned on all the time, but the brain learns to inhibit the one you don't need, said psychology professor Teresa Bajo of the University of Granada in Spain. That's pretty constant activity.

But people don't have to master a new language to benefit some, Bialystok said.

Exercising your brain throughout life contributes to what's called cognitive reserve, the overall ability to withstand the declines of aging and disease.