Longitudinal Detection of Dementia Through Lexical and Syntactic Changes in Writing

Studies of language in dementia have concluded that, along with a general cognitive decline, linguistic features are also negatively affected. Studies of the language of healthy elders also observe a linguistic decline, but one which, in contrast, is markedly less severe than that induced by dementia. In this paper, we examine whether the disease can be detected from the diachronic changes in written texts and, more importantly, whether it can be clearly distinguished from normal aging. Lexical and syntactic analyses were conducted on fifty-one novels by three prolific literary authors: Iris Murdoch, P. D. James, and Agatha Christie. Murdoch was diagnosed with Alzheimer’s disease shortly after finishing her last novel; James, at 89 years of age, continues to publish critically-acclaimed works; Christie, whose last few novels are deemed strikingly subpar compared to her previous works, presents an interesting case study of possible dementia. The lexical analysis reveals significant patterns of decline in Murdoch’s and Christie’s later novels, while James’s rates remain relatively consistent throughout her career. The syntactic measures, though unveiling fewer significant linear trends, discover a cubic model of change in Murdoch’s novels, with a deep decline around her 50s. Our findings provide further support for the hypothesis that dementia, which manifests clearly in lexical features, can be detected in writing. 2