A man experiences memory loss, a side effect of Alzheimer’s disease. Photo courtesy of OHSU Brain Institute

Almost everyone has had the flu at least once in their life. This is because influenza is a contagious respiratory disease that is transmitted through the air and direct contact, making it easy to contract. But Alzheimer’s is different. The incurable disease that results in memory loss and loss of cognitive function is strictly neurological, meaning that it is concentrated in the brain. Scientists have found various proteins in the brain responsible for the disease, in addition to a combination of genes passed down one’s family line. Therefore, Alzheimer’s disease is impossible to contract unless an individual already houses the specific genetic material or proteins, or so we have thought up until now. 

One protein known for causing Alzheimer’s, amyloid, was key for the newest scientific discovery regarding the disease’s transmission. Though most come to have some buildup of amyloid in the brain as they age, enzymes tend to break down the plaque, preventing the buildup from becoming severe. However, about two-thirds of those diagnosed with Alzheimer’s have a more significant buildup of amyloid, which has prompted researchers to assume that there is a connection between the protein and Alzheimer’s disease. But how is amyloid relevant to Alzheimer’s being transmitted?

Until 1985, doctors administered procedures planting growth hormones in the bodies of young children to combat the effects of growth disorders. The hormone injected, though, came from a part of the brain of cadavers, a part called the pituitary gland. (Recall that amyloid can be found in the brain.) Many of the people who received this hormone as part of the procedure that is now illegal were found to have increased levels of amyloid as adults. Of eight people who received the procedure, researchers found that three had already been diagnosed with Alzheimer’s. Scientists hypothesize that this could be due to the accidental injection of amyloid into the patients when the growth hormone was administered, as the hormone originated from the brain, a site where amyloid is common. 

Some scientists are now thinking this is proof of Alzheimer’s being transmitted, something very unexpected, as Alzheimer’s is not a contagious disease. While this discovery presents a very rare instance in which Alzheimer’s was spread, exercising caution in neurological procedures could prevent this from occurring again, as it is unclear if contaminated instruments could transmit Alzheimer’s if a patient with the disease was operated on, too. The recent discovery could change neurological practice and further the ongoing study of the still-mysterious Alzheimer’s disease as a whole, but much about the disease is still left undiscovered.