Bilingualism may delay the onset of Alzheimer's disease, a brain scanning study suggests.
The study by Canadian researchers in the journal Cortex offers the first physical evidence that speaking more than one language delays the onset of disease.
"This is unheard of — no medicine comes close to delaying the onset of symptoms and now we have the evidence to prove this at the neuroanatomical level," Tom Schweizer, a neuroscientist who headed the research, said in a release.
In the study, researchers studied CT scans of 40 people who had been diagnosed with Alzheimer's disease. They all had similar levels of education and cognitive skills, such as attention, memory and planning. Half were fluently bilingual and the other half spoke only one language.
"Bilingualism appears to contribute to increased cognitive reserve, thereby delaying the onset of Alzheimer disease and requiring the presence of greater amounts of neuropathology before the disease is manifest," the study's authors wrote.
Full text continues below slideshow
Find out which everday habits can harm your memory
It's no secret that our diet plays a significant role in our health -- but can it also affect our memory and cognition? A 2009 study at the University of Cambridge found that rats who consumed a high-fat diet took 25 percent longer time to complete a maze than when they consumed a normal diet, suggesting that a high-fat diet can impair cognitive function, at least. Researchers from the University of South Carolina at Charleston arrived at similar results when they found that rats fed a diet high in saturated fat and cholesterol performed poorer and made more mistakes on a similar maze test compared with rats on a low-cholesterol, unsaturated-fat diet. The "low-carb" diet was examined by Tufts University researchers in 2008. The women involved with the study chose either a low-carb diet or a diet meeting the recommended guidelines from the American Dietetic Association. Participants on the low-carb diet performed worse on memory-based tasks than those on the ADA diet.
Numerous studies have linked smoking with memory decline, including one published in the American Journal of Public Health in 2003. This study associated cigarette smoking with faster declines in verbal memory between 43 and 53 years of age. In 2010, researchers from the University of California at San Francisco analyzed studies of the the connection between smoking and Alzheimer's disease. They found that smoking cigarettes was a high risk factor for the disease and nearly doubled a person's chance of developing Alzheimer's. Though smoking is certainly bad for your health, some research has suggested that the nicotine from smoking cigarettes could enhance cognition and memory -- and perhaps play a role in why people become dependent on tobacco products. A 2008 study published in Psychopharmacology looked at a series of literature on the subject, dating from 1994 to 2008. The results suggested that nicotine positively affected several domains of cognition, including short-term episodic memory accuracy, working memory and response time.
As researcher Robert Stickgold pointed out in his 2005 study, the question of how sleep affects our learning and memory is anything but a new concept. But with Americans becoming more and more sleep-deprived -- the Centers for Disease Control and Prevention say that 28 percent of U.S. adults report frequent insufficient sleep -- researchers haven't stopped examining the effects. One 2007 study published in Proceedings of the National Academy of Sciences found that participants who were sleep-deprived for 24 hours had reduced levels of visual short-term memory, but other research suggests that this connection might not apply to everyone. In a 2009 study published in the Journal of Sleep Research, participants aged 14 to 16 years received only four hours of sleep one night, preceded by a nine-hour night of sleep and followed by a nine-hour night of sleep. The adolescents' memory consolidation did not appear to be affected by the change in sleep pattern. However, numerous other studies, like this one from the Journal of the American Academy of Child & Adolescent Psychiatry, suggest otherwise, saying adolescent participants' performance on working memory tasks were hindered by poor or insufficient sleep. Dr. Nelson says an important thing to keep in mind is that it's not the quantity of sleep but the quality of sleep that counts, because certain stages of sleep are more vital for memory consolidation. "You could have someone who gets an adequate number of hours of sleep, but if you interrupt them as they're going into certain cycles you can undercut their memory consolidation," Nelson says.
By now, we all know that exercise is good for us. It can also prevent memory loss as we age, says a study published earlier this year in Proceedings of the National Academy of Sciences. The study sought to determine whether exercise can modify the volume of our hippocampus -- the part of our brain involved with forming memories -- during late adulthood. Researchers found that exercise could do just that, thereby improving memory function. The cool part about this, Dr. Nelson says, is that it seems to convey benefits even for people who are older. The research suggests that it's never too late to begin exercising and improving memory function.
That our memory is hindered by chronic alcohol use and abuse probably seems like a no-brainer. But what about after a "normal" night of social drinking with friends? A 2004 study published in the journal Alcohol and Alcoholism tested participants the mornings after an evening out over a course of several weeks. The researchers found delayed recognition, even though blood alcohol levels were at or near zero at the time of testing, suggesting that memory is impaired after a night of drinking. However, there is some research suggesting that moderate consumption of alcohol can actually benefit brain health, Dr. Nelson says, such as a 2002 study published in The Lancet that suggested that moderate alcohol consumption could reduce the risk of dementia. Dr. Nelson says that this creates a sort of double-edged sword, since consuming too much alcohol can obviously lead to abuse and serious health problems.
Concerned that your daily habits are harming your memory? Check out some of these memory-boosting tips.
But bilingualism does not prevent Alzheimer's, Schweizer noted. Once Alzheimer's symptoms appear in bilingual people, it is not clear whether the disease progresses at an accelerated rate.
He said that because bilingual people constantly switch from one language to another or suppress one language to speak in the other, their brains may be better prepared to compensate through enhanced brain networks or pathways when Alzheimer's sets in. The study was done in Toronto, where the second language of many study participants was French, English or Chinese.
Schweizer said the results are especially important in Canada, which is officially bilingual and has large numbers of immigrants for whom French and English are at least second languages.
The investigators considered the possibility that factors other than bilingualism contributed to the difference.
But both years of education and occupational status were greater in those speaking one language, which the researchers said works against their hypothesis.
Previous studies by the same team suggested the delay in onset of Alzheimer's was not affected by immigrant status.
Researchers still don't know precisely how bilingualism offers an advantage in delaying the disease.
They cautioned that the findings should be interpreted cautiously given the relatively small sample sizes.
The next steps would be to repeat the study in a larger sample of patients followed over time using more sophisticated MRI technology, the researchers said.
More studies are also needed to find you whether a second language has to be learned early in life to provide maximum benefit.
The study was funded by the Alzheimer Society of Canada and the Canadian Institutes of Health Research.