Researchers at the University of Sydney discovered that Australians born overseas who spoke a first language other than English could tolerate neurodegeneration longer before behavioral variant FTD (bvFTD) symptoms begin to show, according to a study published in the Journal of Neurology.

“Our findings suggest that current diagnostic methods might be less accurate at identifying symptoms in Australians from culturally diverse backgrounds,” said Amira Skeggs, the lead investigator of the study. “When it comes to neurodegenerative syndromes like bvFTD, culturally diverse people can have a later onset of the disease compared to monolingual Australians because they have other factors which could increase their resilience or cognitive reserve.”

The authors then present the “cognitive reserve hypothesis,” which proposes that people from non-English speaking backgrounds maintain a more extensive cognitive reserve due to bilingualism, among other factors. This “reserve” hypothetically allows them to endure disease progression for longer before symptoms typical of bvFTD begin to show.

To evaluate the validity of the hypothesis, researchers recruited 158 participants from FRONTIER, the largest FTD specialist clinic in Australia. 51 of the participants were volunteers without FTD who served as controls. All of the participants in the study took part in a comprehensive exam that included a neuropsychological assessment, an MRI scan, and screening by a behavioral neurologist.

Researchers employed a common cognitive exam to assess participants. They used other examinations to check things such as memory and attention before running the results through a series of statistical analyses.

There were no significant differences between disease duration, the age of diagnosis, or the severity of bvFTD. While not considered statistically significant, researchers noted that the age of onset for people with a first language other than English was older.

More significant were the scores for non-verbal assessments. “Comparisons revealed that the group who spoke a non-English first language performed worse than the other groups on verbal tests but better on non-verbal tests,” said Skeggs. “The poor verbal performance in the non-English speaking group is probably influenced by cultural biases within current clinical tests, so the reason they are showing decline may not actually be because they are declining.”

The cultural bias within current clinical tests poses a significant problem for diverse populations worldwide, the researchers said. Without adjusting criteria for non-Western languages and cultures, Skeggs notes that “it can be difficult to diagnose the diseases in non-Western people because they may not have the same symptoms.

“There is also some evidence that non-English-speaking patients are diagnosed at a later age, potentially due to a delay in clinical diagnosis or cognitive reserve slowing the disease onset,” Skeggs said.

The study notes the pressing need to include diverse populations in FTD research to address the roots of these diagnostic shortcomings, such as how FTD’s presentation changes across cultures.

Did you know that researchers have also conducted studies evaluating the efficacy of cognitive exams? Click here to learn more.