A recent study published in Neurology from scientists at the University of California San Francisco Memory and Aging Center (CA, USA) has suggested that English and Italian speakers who have dementia-related language impairments may experience distinct kinds of speech and reading difficulties based on features of their native languages.
Until recently, it was believed that brain diseases that impact language abilities would manifest in the same way in patients across the globe. However, recent studies are beginning to question this. For instance, in comparison with English or French speakers, Italian speakers with dyslexia have been noted to have less severe reading impairments due to the much simpler and more phonetic spelling in Italian.
“Clinical criteria for diagnosing disorders that affect behavior and language are still mainly based on studies of English speakers and Western cultures, which could lead to misdiagnosis if people who speak different languages or come from another cultural background express symptoms differently,” explained senior author of the study, Maria Luisa Gorno-Tempini (University of California San Francisco).
Within the small study, researchers focused on individuals with primary progressive aphasia (PPA). They recruited 20 English-speaking participants with PPA and 18 Italian-speaking participants with PPA, all of whom had the non-variant form (difficulty producing or pronouncing words).
When cognitive tests and MRI brain scans were compared, the researchers reported that similar cognitive function and comparable levels of brain degeneration were present in both groups. However, upon comparing performance based on linguistic tests, the team observed a key difference.
English-speaking participants with PPA were noted to have more trouble pronouncing words – a traditional hallmark of non-fluent PPA – and spoke less than usual. On the other hand, Italian-speaking participants with PPA had less difficulties with pronunciation but produced much shorter and grammatically simpler sentences.
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Gorno-Tempini commented that: “We think this is specifically because the consonant clusters that are so common in English pose a challenge for a degenerating speech-planning system. In contrast, Italian is easier to pronounce, but has much more complex grammar and this is how Italian speakers with PPA tend to run into trouble.”
The results of the study are important for efforts to ensure that diagnoses for people with PPA across different countries and cultures are accurate. In the current study, the investigators mentioned how the Italian speakers did not match the established diagnostic criteria for non-fluent PPA as closely as the English speakers, as the criteria is based on studies of English-speaking participants.
“This means that there are probably many more people around the world – including non-native English speakers in the US – who are not getting the right diagnosis because their symptoms don’t match what is described in clinical manuals based on studies of native English speakers,” concluded Gorno-Tempini.
The researchers cautioned that their results were obtained from a small study and cannot completely exclude confounding factors, such as dementia severity, undetected anatomical differences and differences in education levels between Italian- and English-speaking participants.
Sources: Canu E, Agosta F, Battistella G et al. Speech production differences in English and Italian speakers with nonfluent variant PPA. Neurology doi:10.1212/WNL.0000000000008879 (2019); www.ucsf.edu/news/2020/01/416406/speech-disrupting-brain-disease-reflects-patients-native-tongue