Researchers in the U.K. may have uncovered evidence that Alzheimer's disease can be transmitted via some medical procedures.
Five patients who had received a cadaver-derived pituitary growth hormone injection during childhood developed Alzheimer's, the investigation, published Jan. 29 in Nature, revealed.
The hormone given in the injection was extracted from the pituitary glands of cadavers' brains, but at the time, scientists were not aware that what was being extracted from the pituitary glands was also the amyloid-beta protein, which is the same protein known to cause plaque in the brain of Alzheimer's patients.
The procedure is no longer used after separate research emerged linking it to another neurological illness called Creutzfeldt-Jakob disease.
The possibly contaminated injections were given to around 27,000 children — 7,700 of whom were in the U.S. — from 1959 to 1985, NBC News reported.
Researchers ruled out other possible causes of Alzheimer's in the patients, including ruling out childhood intellectual conditions, underlying diagnoses, a lack of the given growth hormone and cranial radiotherapy.
"Taken together, the only factor common to all of the patients whom we describe is treatment with the HWP subtype of c-hGH," the authors of the study wrote. "Given the strong experimental evidence for Aβ transmission from relevant archived HWP c-hGH batches, we conclude that this is the most plausible explanation for the findings observed. The clinical syndrome developed by these individuals can, therefore, be termed iatrogenic Alzheimer's disease, and Alzheimer's disease should now be recognized as a potentially transmissible disorder."
Importantly, the findings do not mean that Alzheimer's is a contagious condition in the way COVID-19 or other infections are.
"The actual risk of transmission of Alzheimer’s disease in this context is really very low and these are probably going to be very rare cases," John Collinge, MD, lead study author and a neurologist and the director of the University College London Institute of Prion Diseases told NBC News.