Alzheimer's disease may be transmitted from one human to another, according to a new study. However, it is not transmitted through contact with a person who has the disease, but through a treatment, Live Science reported.
From 1958 to 1985, about 30,000 people who had short stature received shots of a human growth hormone taken from the pituitary glands of cadavers. This practice was stopped in 1985 when it became apparent that some of the hormones were infected with Creutzfeldt-Jakob disease (CJD) and transmitted CJD to others.
A small study involving autopsies of eight people who died from CJD showed that their brains contained significant deposits of amyloid beta protein, a protein that is often found in Alzheimer's patients but not in CJD patients. The researchers said that this finding suggested that the source of the growth hormone possibly had Alzheimer's disease and transmitted it to those who received the shots.
"This was very surprising," University College London professor and lead study author John Collinge said, according to Reuters. He noted that previous animal studies showed evidence that the process could be done. "There is evidence from animal studies that it is not implausible."
Four of the eight brains had large amounts of amyloid protein, while two brains had patchy yet considerable amounts. Only one brain did not have any trace of the protein.
Collinge clarified that the study was just "an observational study" and was not conclusive in itself that Alzheimer's disease can be "induced" in a person by contact with an infected person's brain tissue.
"We're simply describing what we see in these patients and we are trying to explain that," he said, according to Scientific American.
Some scientists believe that the new finding is an important contribution in the research of neurodegenerative diseases like Alzheimer's being induced by misfolding proteins.
"The best evidence for the transmissibility of amyloid-beta lesions comes from animal studies, in which various factors are carefully controlled and competing hypotheses are ruled out," said Emory University neuroscientist Lary Walker, who was not involved in the study, according to Scientific American. "[This study] adds an important dimension to the establishment of the prion paradigm."
However, other scientists say that the study does not provide enough evidence to prove that Alzheimer's is transmissible.
"While this is a beautiful piece of investigative medicine, we have to keep the findings in context," Masud Husain, Oxford neurology specialist, told Reuters. "These results certainly do not provide sufficient evidence to believe Alzheimer's disease is a transmissible illness."
The study was published in the Sept. 9 issue of the journal Nature.
