Researchers in Italy have studied bilingual people with mild Alzheimer’s to understand how speaking two languages daily throughout life could be beneficial by increasing their so-called ‘cognitive reserve’. The study is published today in PNAS.
Previous studies have shown that people who are bilingual show symptoms of Alzheimer’s disease and other dementias later than people who speak just one language – around a 4.5-year delay. It has been suggested that this is due to bilingual people having a greater cognitive reserve, meaning that their brains are more resilient to the damage taking place in Alzheimer’s.
In this new study, a team of researchers looked at the changes in the brain that could explain this phenomenon. They studied a group of 85 people with mild Alzheimer’s disease (disease duration <3 years), 45 of whom were classed as bilingual and used German and Italian daily due to where they live in Northern Italy. The volunteers underwent brain scans to measure energy usage in their brains and tests of their memory and thinking skills. They also completed a language background questionnaire from which a bilingualism index was calculated, which provided a measure of the extent to which each person used language each day.
The team found that although the bilingual individuals were on average 5.71 years older and had fewer years of education, they performed better on the memory and thinking tests. The damage that occurs in key brain regions in people with Alzheimer’s reduces how much energy these areas of the brain can use, and interestingly those participants who were bilingual showed lower energy use in these areas than the volunteers who spoke one language. The scientists also found that more energy was used in other brain regions in the volunteers who were bilingual, and that these people also had greater brain connectivity, supporting the idea that these people’s brains were able to compensate for the damage occurring due to Alzheimer’s disease. Using the bilingualism index, the team found that the greatest benefit was seen in people who were lifelong fully bilingual, and used both German and Italian equally each day.
Dr David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK, said:
“Cognitive reserve is thought to explain why some people’s brains are more resilient to damage than others, and there is increasing evidence that being bilingual throughout life could increase our cognitive reserve. This new study looked at people with mild Alzheimer’s who are lifelong bilinguals and use two languages, German and Italian, in their daily lives in Northern Italy. While other studies have indicated that bilingualism can delay the onset of dementia symptoms, this study goes further, showing that there are differences in the brains of people with Alzheimer’s who are fully bilingual that could explain why they are resilient to damage.
“It’s important to note that these benefits were seen in people who use two languages on a daily basis throughout their lives, so the findings can’t be extended to those who are non-fluent and occasionally speak a second language. The findings lend weight to the theory that keeping the brain active may provide a form of cognitive reserve, helping to delay the onset of symptoms as diseases like Alzheimer’s develop. In addition to keeping mentally active, the best current evidence shows that not smoking, eating a healthy diet, taking regular exercise, only drinking in moderation and keeping blood pressure and cholesterol in check can all help to keep our brains healthy as we age.”