Terry Pratchett's "The Last Continent" May Have Contained Subtle Alzheimer's Clues, 10 Years Before His Diagnosis

Pratchett was a respected English author, best known for his Discworld series of fantasy-comedy books, spanning 41 novels. In 2007, he announced that he had a rare form of early-onset Alzheimer's disease, branding it "an embuggerance". While he continued his life as best as he could, writing seven further books before his death in 2015, Pratchett spoke of the terrible nature of the disease, and how others reacted to him following his diagnosis.

“It seems that when you have cancer you are a brave battler against the disease, but when you have Alzheimer’s you are an old fart," he said of his experience. "That’s how people see you. It makes you feel quite alone.”

In his final years, he became an advocate for awareness of the disease, as well as dementia research.

Pratchett himself believed that he may have been aware of early signs of the disease in the year prior to his diagnosis.

"When I look back now, I suspect there may be some truth in the speculation that dementia (of which Alzheimer’s is the most common form) may be present in the body for quite some time before it is capable of diagnosis," he wrote in The Guardian, adding that he sought medical advice in 2007 after finding, "my typing had been getting progressively worse and my spelling had become erratic".

In a new study, researchers in the UK have found evidence that early signs of dementia may have been detectable years before his diagnosis in 2007.

"Dementia is often described as a condition of memory loss, but this is only part of the story. In its earliest stages, dementia can affect attention, perception and language before memory problems become obvious. These early changes are difficult to detect because they are gradual and easily mistaken for stress, ageing or normal variation in behaviour," the team explains in an article for The Conversation.

"Language, however, offers a unique window into cognitive change. The words we choose, the variety of our vocabulary and the way we structure description are tightly linked to brain function. Even small shifts in language use may reflect underlying neurological change."

The team analyzed the language used by Pratchett in his Discworld novels and how that language changed over time. They paid particular attention to “lexical diversity”, or how much variety there was in the author's choice of words, as well as adjectives used in the novel.

The team found that there was a "significant decrease in lexical diversity (TTR)" for both nouns and adjectives in Pratchett's later works. Though the team stresses that this did not mean that the quality of the works dropped off, they found that the language subtly shifted, with the richness of descriptive language gradually narrowing.

"Crucially, the first significant drop appeared in The Last Continent, published almost ten years before Pratchett received his formal diagnosis," the authors explain. "This suggests that the 'preclinical phase' of dementia – the period during which disease-related changes are already occurring in the brain – may have begun many years earlier, without obvious outward symptoms."

While people's language is highly variable and subject to changes, the team suggests that language analysis could help detect early risk of dementia. As well as being quite available – people write messages, emails, reports all the time, even if they aren't award-winning novelists – language analysis is also cost-effective, and non-invasive on the patient. 

However, the team stresses that the findings of the study may not be generalizable, as they are focused on a single author, and may be specific to Pratchett, or that the changes may be a sign of natural aging. Still, studies of other authors have found their language did not show similar shifts well into their 80s, suggesting Pratchett's changes may have been due to a condition, rather than aging. 

"The results also emphasise that language deficits may be observed many years before a formal diagnosis and indicate that Alzheimer’s disease has a long preclinical period—in the case of Terry Pratchett, potentially almost ten years," the researchers conclude in their study. "Further research is now needed to explore the full potential of linguistic analysis as a diagnostic tool for dementia."

The study is published in Brain Sciences.