New research suggests that Alzheimer’s can be spread from one human to another in case of rare medical accidents, but experts say there is no evidence that the season can be passed between people through everyday activities or routine care.
Researchers say a handful of people who received human growth hormone from the pituitary glands of deceased donors have gone on to develop early-onset Alzheimer’s, likely because the hormones used were contaminated with proteins that bred the brain disease.
“We’re not suggesting for a moment you can catch Alzheimer’s disease. This is not transmissible in the sense of a viral or bacterial infection,” said Prof John Collinge, co-author of the study and director of the MRC Prion Unit.
“It’s only when people have been accidentally inoculated, essentially, with human tissue or extracts of human tissue containing these seeds, which is thankfully a very rare and unusual circumstance.”
Writing in the journal Nature Medicine, Collinge and colleagues report how between 1959 and 1985, at least 1,848 patients in the UK received human growth hormone extracted from the pituitary glands of cadavers
However, the practice was banned in 1985 after it was determined that some patients subsequently had Creutzfeldt-Jakob disease (CJD) as a result of hormone samples contaminated with CJD-causing proteins.
Of the 80 such cases in the UK, some were also found to have a protein called amyloid-beta in their brains when they died – a hallmark of Alzheimer’s disease.
Andrew Doig, professor of biochemistry at the University of Manchester, said experts were already very careful about transmitting brain tissue between people.
“While the new type of Alzheimer’s reported here is of great scientific interest, as it reveals a new way to spread the disease, there is no reason to fear it, as how the disease was caused was stopped over 40 years ago,” Doig said. “Disease transmission from human brain to brain in this way should never happen again.”