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Alzheimer’s disease is one of the United States’ top ten causes of death but the only one on the list with no known cure. Alzheimer’s is actually the third leading cause of death after cancer and heart disease. About 5.7 million people in the U.S. have Alzheimer’s disease and the rate is expected to triple to 16 million by 2050.

A new study published in the Journal of Alzheimer Disease and Associated Disorders looked at the conversion rates of mild cognitive impairment to Alzheimer disease in monolingual and bilingual patients.

“Our study provides further evidence that lifelong bilingualism provides protection against symptoms of dementia in older age,” study author Ellen Bialystok told us. Bialystok is a distinguished research professor and Walter Gordon York research chair in lifespan cognitive development at the department of psychology at York University in Toronto, Ontario, Canada.

“We already knew from previous studies that bilinguals show symptoms of dementia at a significantly older age than comparable monolinguals matched on relevant variables and once dementia has been diagnosed, bilinguals who present the same degree of symptoms have more disease in their brains than comparable monolinguals but are able to function at higher levels than monolinguals with that amount of disease burden,” Bialystok told us. “The next question, therefore, was whether the decline after diagnosis would be more rapid for bilinguals than monolinguals, given that they have more disease.”

According to the World Health Organization, there are approximately 50 million people around the globe living with dementia. Symptoms of dementia include being easily distracted, and an inability to process information as quickly. Other symptoms include difficulty recalling names of family and friends, lack of inhibition, poor judgment, and in people who are bilingual, regression to their primary language.

“The predictions were based on the theory of cognitive reserve. From that perspective, individuals with more resilience, such as bilinguals, would decline more rapidly after a clinical threshold of disease burden had been crossed,” Bialystok told us. “The question provides new and important evidence in understanding cognitive reserve and whether bilinguals indeed accumulate cognitive reserve throughout life that is ultimately protective against symptoms of dementia.”

Bilingualism is on the rise in the U.S. Data in recent years indicates about 20 per cent of Americans are bilingual, doubling the rate when second language information began collection in 1980. Though on the rise, the U.S. rate of bilingualism is lower than other countries including Israel, the country with the highest rate of bilingualism among its population at 74.7 per cent.

“We identified patients who had been diagnosed with mild cognitive impairment, generally considered to be a precursor of Alzheimer’s disease and followed their progress through their six-month interval appointments until the clinical staff had determined that their new diagnosis was Alzheimer’s disease, not mild cognitive impairment,” Bialystok told us. “The relevant variable was the length of time I took for the diagnosis to change from mild cognitive impairment to Alzheimer’s disease.”

The top five bilingual countries in the world are Israel, Egypt (68 per cent), Indonesia (57 per cent), Saudi Arabia (53 per cent), and Sweden (51 per cent).

Interestingly, though bilingualism is found to help protect against dementia, researchers of the current study found that bilingual patients converted more rapidly to Alzheimer’s disease.

“We presume this is because they already had more disease in their brains and could no longer continue functioning at the high levels they had managed to that point,” Bialystok told us. “It was the predicted result. This adds to the evidence that bilingualism is a source of cognitive reserve. At present, there are no effective pharmacological treatments for Alzheimer’s disease and none currently imminent. Lifestyle experiences that build cognitive reserve are the best defence at the moment for dealing with dementia.”