A simple vocabulary test could improve early diagnosis of Alzheimer's disease, a new study has shown.
British scientists have discovered that people routinely forget seldom-used words when they enter the initial stages of the disease.
Early diagnosis of Alzheimer's is vital to ensure patients receive the full benefits of treatment, which can slow the progress of dementia.
Andy Ellis, a psychology professor from the University of York, and colleagues from Hull and Aberdeen universities have investigated how the vocabulary of Alzheimer's patients diminishes.
They asked 96 Alzheimer's patients and 40 similarly aged healthy volunteers to list as many animals as possible in one minute. They were then asked to list types of fruit in the second minute.
Evidence of a shrinking vocabulary in Alzheimer's patients was clear. They could only list between ten and 15 types of animal or fruit on average, while the healthy controls reached 20 to 25.
The Alzheimer's patients appeared to have lost some words, for example "badger", "giraffe" and "zebra".
Professor Ellis explained that healthy people find it much easier to recall words that are familiar, if they are encountered regularly in everyday life and if they are learned in early childhood. Words like "cat" and "dog" fall into this category.
And Alzheimer's patients tend to "lose" the more challenging words, learned later in childhood or adulthood and less frequently used, such as "badger" and "zebra".
This pattern was so consistent that Professor Ellis believes it can be used to develop a very simple diagnostic test for the disease.
Speaking in Dublin at the British Association's Festival of Science he said this "might alert GPs to the fact that something is beginning to go wrong".
At present doctors use memory tasks to detect Alzheimer's and Professor Ellis said that the word test might provide a useful alternative as it probes a different area of the brain.