Weekly feature: effects of language on dementia

Written by Science

A new study on patients with dementia, conducted by the University of California, has discovered that the disease affects patients differently depending on the language they speak.

Dementia is an umbrella term used to describe a number of progressively declining conditions affecting the brain, including Alzheimer’s Disease. All forms of dementia damage neurones in the brain, meaning its communication with the rest of the body is ineffective and resulting in cognitive function and memory impairment. Dementia sufferers can also suffer from aphasia, a difficulty with the production and comprehension of speech.

The study in question compared English speakers with Italian speakers, and assessed how dementia had affected their language skills. MRI scans of the participants’ brains revealed similar levels of cognitive activity, despite the eventual differences in results of the study.

It was found that English speakers tended to speak less than usual when suffering from dementia, and to have difficulty pronouncing words. This condition is known as Broca’s Aphasia, and is shown by a language production deficit.

Italian speakers, in comparison, tended to pronounce words more accurately, but had difficulty producing grammatical sentences. This is closer to the condition known as Wernicke’s Aphasia, which causes sufferers to have difficulty with language comprehension. Their utterances are pronounced correctly, but are often inappropriate for the context of a conversation.

Researchers who conducted the study concluded that these issues could be caused by the differing complexity of the languages’ phonology. English has many complex consonant clusters (sounds in which several consonants are grouped together, i.e. at the start of ‘blister’), which are said to be difficult for dementia sufferers to produce accurately. Italian is said to be comparatively easier to pronounce, due to its simpler phonology. However, Italian’s grammatical rules are more complex than English, meaning dementia sufferers find it difficult to produce a grammatical sentence. The differences in the languages’ phonological and grammatical properties most likely stems from the fact English is a Germanic language, whilst Italian is a Romance language.

Currently, the scientific community tends to assume dementia-induced Aphasia affects all patients in the same way as it affects English patients, since the majority of studies are conducted on English speakers. This means that if someone does not show symptoms that match the behaviour of a typical English-speaking patient, they might not be diagnosed with dementia. Yet, the findings of this study suggest that, if the patient in question is not a native English speaker, they might actually have the disease after all.

In the future, scientists hope to build on this research by comparing an even more diverse array of dementia sufferers speaking different native languages with English speakers, including patients who speak Arabic. They also want to determine whether the level of education a patient has attained affects how quickly Aphasia takes hold.

Last modified: 24th February 2020

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