Linguistic markers of dementia
Researchers from NUS believe that changes in language may be early neurological markers of cognitive decline, and take a structural approach to language in dementia.
| By Professor Bao Zhiming |
The world’s population is ageing rapidly, with the first wave of post-war baby boomers having already reached the age of 70. The World Health Organization estimates that 5-8 per cent of the general population aged 60 and over suffer from various forms of dementia. The actual number is staggering: 50 million people worldwide suffer from the disease, with 10 million new cases diagnosed each year.
The situation is especially severe in Singapore, where nearly 820,000 Singaporeans are aged 60 and older. In 2018, the Alzheimer’s Disease Association of Singapore put the number of Singaporeans who suffer from dementia at 82,000. It has been estimated that the annual cost of care per patient in Singapore exceeds S$70,000, or more than S$5 billion in total.
There is no cure for dementia. Medication is available to improve symptoms, however cognitive decline and memory loss generally persist as patients age.
Early diagnosis is an important step in slowing cognitive decline. Traditionally, diagnosis is made following neuropsychological as well as neurological tests. These include MRI or PET scans that determine brain function, and look for deposits of beta-amyloid protein — a biochemical marker of Alzheimer’s disease. Ultimately however, the onset of dementia is manifested earliest when patients present with signs of confusion, a loss of short-term memory, and the inability to carry out everyday tasks. Recent research is also revealing that changes in a person’s use of language during every day communication may be indicative of an onset of dementia.
Cognition and language are intimately connected. How dementia is manifested in language is a matter of intense research around the world by neuropsychologists, linguists and more recently, by specialists in artificial intelligence who comb through language data for telltale signs of dementia. Parts of speech, word recall, propositional density are among the linguistic features that have been investigated in relation to dementia, with conflicting results.
At NUS, neuropsychologists at the Mind-Science Centre and linguists at NUS English Language and Literature are joining forces to canvas the cognitive and linguistic capabilities of senior Singaporeans in the hope of discovering linguistic markers of dementia, especially in the early stage of the dreadful disease.
The researchers believe that changes in language may be early neurological markers of cognitive decline, and take a structural approach to language in dementia. Structurally complex sentences require more cognitive resources to process. The onset of cognitive decline, it is hypothesised, may cause a parallel decline in the use of sentences with complex structures, resulting in language deficits that solidify as the disease progresses.
The use of language is often varied between individuals. Regional and social differences play a significant role in this variability and this is especially true in a Singapore context. With four official languages, and a unique blend of various dialects influencing local English, Singapore provides a unique environment in which to conduct this research. Not only will the outcomes provide new avenues of care for Singapore’s ageing population, but the methods used to identify linguistic markers of dementia will serve as a foundation that can be applied to other English dialects around the world.
An interdisciplinary team at NUS is now combing through the spontaneous speech data collected from Singaporeans, looking for linguistic markers of dementia. Once established, these markers can serve as tools for early diagnosis, and for developing linguistic therapies that address specific language deficits.
About the author
Prof Bao Zhiming is Provost's Chair from NUS English Language and Literature. He is a theoretical linguist working in the areas of contact linguistics and theoretical phonology.