A study by researchers at Harvard Medical School has suggested that delirium could speed up the progress of Alzheimer's disease. The study of 408 people with Alzheimer's disease, compared those people who had had an episode of delirium with those who had not and found that the mental capabilities of those who had been delirious declined nearly twice as quickly. Delirium is a state of mental confusion in which people's speech becomes disordered and nonsensical and they experience hallucinations. It is potentially preventable so by stopping people from developing delirium the researchers hope that this might reduce the speed of people's decline.
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