Abundant research has shown that learning a second language can boost brain power, but a new study suggests that the effects extend to those who begin in middle childhood.

It shows that people who began learning English at age 10 and were immersed in the language, meaning they heard and used it in daily life, showed improvements in the structure of the brain's white matter compared with people who grew up speaking only English and did not learn a second language.

These "higher levels of structural integrity" were in areas responsible for language learning and semantic processing, which occurs when the meaning of a word is encoded and related to similar words with similar meaning.

The findings, published in the Proceedings of the National Academy of Sciences on Monday, studied brain scans from 20 people, all around the age of 30, who had lived in Britain for at least 13 months. They had all started learning English as a second language around age 10.

Their imaging analyses were compared with 25 people of similar age who spoke only English. The study was led by Christos Pliatsikas of the University of Kent School of Psychology in Britain.

"Everyday handling of more than one language functions as an intensive cognitive stimulation that benefits specific language-related brain structures by preserving their integrity, and therefore it protects them against deterioration in older age," the study found.