A study of Harold Wilson's language at the dispatch box has supported suggestions that he was suffering the early stages of Alzheimer's disease when he resigned unexpectedly as Prime Minister.

The analysis, which looked at the former Labour leader's use of a group of common words, hints at a decline in his oratorical skills from 1965 to 1976.

Analysis of Mr Wilson's language during the 1960s, when he was in his first term of office, showed that he was less reliant on commonly used words than his parliamentary colleagues.

By the mid-1970s, however, the originality of his language had declined, to become much more prosaic.

The study into Mr Wilson's speech patterns was carried out by Peter Garrard, Reader in neurology at the University of Southampton. He has previously demonstrated Alzheimer's-like changes in Iris Murdoch's writings.

Dr Garrard said: “What changes is the distinction between the general speakers and the vocabulary spoken by Harold Wilson. In his first two periods of office, there was clear blue water between [him and] them. In the last period he had moved closer to general linguistic use.”

However, Dr Garrard said it was too early to be certain that it was Alzheimer's that had caused the deterioration in the Prime Minister's linguistic standards. It could, he said, be down to other reasons, such as unconsciously changing his language to match his colleagues.

The technique used in the study, published online in the Journal of Neurolinguistics, is being developed to help reseachers learn about the onset of Alzheimer's disease.

Dr Garrard said that if the computer analysis can be shown to work effectively it might yield giveaway signatures of Alzheimer's in people's use of language, which could, perhaps, be used to help to diagnose the disease.

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