# Detecting Dementia Using Lexical Analysis: Terry Pratchett’s Discworld Tells a More Personal Story

## TL;DR

This study uses Terry Pratchett's writing to detect early signs of dementia through changes in language patterns, suggesting cognitive decline may be visible years before diagnosis.

## Contribution

The study demonstrates that linguistic analysis of an author's work can reveal early signs of dementia, potentially years before clinical diagnosis.

## Key findings

- A significant decrease in lexical diversity was observed in Terry Pratchett's later works.
- The shift in language patterns occurred approximately ten years before Pratchett's dementia diagnosis.
- Total wordcount increased while lexical diversity decreased, indicating simpler language use.

## Abstract

Background/Objectives: Dementia, characterised by cognitive decline, significantly impacts language abilities. While the risk of dementia increases with age, it often manifests years before clinical diagnosis. Identifying early warning signs is crucial for timely intervention. Previous research has demonstrated that changes in language, such as reduced vocabulary diversity and simpler sentence structures, may be observed in individuals with dementia. This study investigates the potential of linguistic analysis to detect early signs of cognitive decline by examining the writing of Sir Terry Pratchett, a renowned author diagnosed with Posterior Cortical Atrophy (PCA), typically a form of dementia caused by Alzheimer’s disease. Methods: This study analysed 33 Discworld novels by Terry Pratchett, comparing linguistic features before and after a potential turning point identified through analysis of adjective type-token ratios (TTR). Results: A significant decrease in lexical diversity (TTR) was observed for nouns and adjectives in later works. Total wordcount increased, while lexical diversity decreased, suggesting a shift towards simpler language. This shift coincided with a decrease in adjective TTR below a defined threshold, occurring approximately ten years before Pratchett’s formal diagnosis. Conclusions: These findings suggest that subtle changes in linguistic patterns, such as decreased lexical diversity, may precede clinical diagnosis of dementia by a considerable margin. This research highlights the potential of linguistic analysis as a valuable tool for early detection of cognitive decline. Further research is needed to validate these findings in larger cohorts and explore the specific linguistic markers associated with different types of dementia.