Signs of the dementia that author Terry Pratchett died with may have been present in his writing a decade before he was officially diagnosed, according to an analysis of his work.
Pratchett was the author of 41 Discworld fantasy novels, along with numerous other books. He died 10 years ago this week, with posterior cortical atrophy (PCA), a type of dementia caused by Alzheimer鈥檚 disease that he was diagnosed with in 2007, at the age of 59.
PCA can cause problems with vision, number recognition and literacy, which can result in changes to people鈥檚 speech and what they write, as they struggle to recall specific words and opt for more generic options like 鈥渢hing鈥� or 鈥渄o鈥�. Indeed, vision problems led to Pratchett鈥檚 diagnosis in 2007, after he approached his assistant Rob Wilkins and said, 鈥淭he S on my keyboard has gone鈥� Come on, what have you done with it?鈥� The S was still there, though.
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To see if any earlier clues of dementia were turning up in Pratchett鈥檚 writing, at Loughborough University, UK, and his colleagues analysed the text of 33 of Pratchett鈥檚 Discworld books, 29 written before his 2007 diagnosis and four after.
The researchers found a significant decrease in the diversity of nouns and adjectives in later works and also an increase in total world count, which suggests a shift towards simpler language. For example, the average number of verbs used in the book increased from 20,015 to 26,405, but a measure of the diversity of verbs used dropped from 0.078 to 0.067.
However, looking further back through the books, the researchers found that a drop in lexical diversity occurred almost 10 years before Pratchett鈥檚 official diagnosis. The change, says Wilcockson, seems to become evident in , which was published in May 1998. 鈥淭his demonstrates a long preclinical period of dementia and the subtle impairments that aren鈥檛 necessarily picked up by traditional cognitive tests,鈥� says Wilcockson.
The team used a similar approach to , which found comparable changes in the writing of Iris Murdoch 鈥� who died with Alzheimer鈥檚 disease 鈥� and Agatha Christie, who was suspected to have it.
鈥淚t鈥檚 not surprising that they found something,鈥� says at Dalhousie University in Halifax, Canada. 鈥淲e already knew that Terry Pratchett had dementia.鈥� He thinks a more detailed analysis could look at other linguistic factors, such as the ratio of nouns to pronouns. 鈥淭he idea is that if people can鈥檛 remember the name of somebody or something, they use 鈥榠t鈥� or 鈥榟e鈥� or 鈥榮he鈥� more often, which can be a minor indicator of loss of memory or executive function,鈥� says Rudzicz.
Wilkins, who now manages the Pratchett literary estate and is the author of , says the idea of finding when signs of his dementia were first appearing is fascinating, but there are confounding factors.
鈥淏ecoming THE Terry Pratchett took its toll,鈥� he says, 鈥渁nd even though the writing was always at the forefront of what we did, there were now a thousand and one other distractions taking us out of the office on an almost daily basis. Cramming a novel in became harder and harder.鈥�
The year 1998 could have been a tipping point in that process, says Wilkins. 鈥淚鈥檇 been a fan of Terry鈥檚 forever, but seeing him close up at the Discworld convention in 1998, there seemed to almost be a clumsiness to him then. He always had so many things that he was processing.鈥�
Wilkins says that, in hindsight, the first time he started seeing things that might hint at PCA was during the writing of , which could have started as early as 2000, roughly when Pratchett started dictating his novels for Wilkins to type rather than typing them himself.
鈥淚 passed him a cup of tea and he鈥檇 start tapping the table in front of him. I remember on one occasion, I said 鈥榳hat actually is that?鈥�, and he said 鈥榃ell, obviously you have to make sure there鈥檚 a solid surface to put it on.鈥� At the time, I just thought it was his eyesight,鈥� says Wilkins.
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