Alzheimer's isn't exactly contagious, but a protein that goes on to form the disease was perhaps passed to patients during surgery, meaning there could be an acquired form of the disease, a new study finds. UK researchers, who describe their finding in Nature, studied the brains of eight people 36 to 51 who died of Creutzfeldt-Jakob disease, caused by proteins known as prions, or "proteinaceous infectious particles," per Popular Science. They found all had contracted the disease via accidental exposure to prions when they were given a contaminated growth hormone to treat growth problems, reports Reuters. But researchers also discovered something else: "What we found, very much to our surprise, was that of the eight patients, four had quite significant, some severe, deposition of amyloid protein, the Alzheimer's protein," neurologist John Collinge says, per Time. Only one patient showed no sign of the protein.
That doesn't mean Alzheimer's can be passed through normal contact. Instead, it shows that Alzheimer's may, like CJD, be caused by exposure to a protein—in this case, amyloid—that could potentially be passed via surgery. Some researchers argue the amyloid protein's precursor, a-beta amyloid, does "stick avidly to metal surfaces." The human growth hormone given to patients, "in addition to being contaminated with CJD, probably also was contaminated with a-beta seeds," Collinge says; it had been donated by elderly patients after their deaths. Since 1985, human hormone injections have been replaced with synthetic ones due to the risk of contamination. Collinge says research will be needed to ensure other procedures, like blood transfusions, don't raise a person's chance of developing Alzheimer's, but, as another researcher says, "I don't think we need to worry excessively." (Could Alzheimer's be linked to pollution?)