In a significant scientific breakthrough, researchers have uncovered the first evidence of Alzheimer’s disease transmission in living individuals. A recent study published in Nature Medicine details a unique case where Alzheimer’s appears to have been transmitted medically through the amyloid-beta protein. This discovery challenges the traditional view of Alzheimer’s as primarily a sporadic or inherited condition, opening new pathways for understanding the disease.

Alzheimer’s disease is typically seen as either a condition of late adulthood or one resulting from genetic mutations. However, this study highlights an extraordinary scenario: the transmission of Alzheimer’s through a medical treatment involving a specific type of human growth hormone (c-hGH). This hormone, derived from pituitary glands of deceased individuals, was used between 1959 and 1985 to treat childhood short stature. In the UK alone, at least 1,848 people received c-hGH treatment during that period.

The hormone was withdrawn from use in 1985 after it was discovered that some batches were contaminated with prions, infectious proteins that cause Creutzfeldt-Jakob disease (CJD). Synthetic growth hormone replaced c-hGH to eliminate this risk. In earlier research, scientists had already linked c-hGH to early amyloid-beta deposits in patients with iatrogenic CJD (caused by medical intervention). In 2018, the team confirmed that archived c-hGH samples were contaminated with amyloid-beta and could transmit Alzheimer’s-like pathology when injected into lab mice.

Building on these findings, the researchers proposed that individuals exposed to contaminated c-hGH who did not develop CJD might be at risk of Alzheimer’s. The study examined eight individuals who had received c-hGH during childhood. Five of them developed dementia, with either confirmed Alzheimer’s diagnoses or symptoms that met Alzheimer’s criteria. Remarkably, the onset of neurological symptoms occurred much earlier than expected, with ages ranging from 38 to 55.

Further analysis, including biomarker studies, supported Alzheimer’s diagnoses in two cases, and autopsy results confirmed Alzheimer’s pathology in another. Genetic testing ruled out inherited Alzheimer’s disease in all five patients who provided samples, suggesting this was not a case of typical late-onset Alzheimer’s.

While c-hGH is no longer in use, and no cases of Alzheimer’s transmission have been linked to other medical procedures, the researchers stress the importance of reviewing safety protocols. Previous medical procedures linked to CJD transmission should be reassessed to prevent the accidental transmission of amyloid-beta.

Professor John Collinge, lead author and Director of the UCL Institute of Prion Diseases, clarified, “There is no suggestion whatsoever that Alzheimer’s disease can be transmitted between individuals during daily life or routine medical care.” The study focused on a discontinued medical treatment involving contaminated materials, and there is no evidence to suggest routine medical or social care poses a transmission risk.

While these cases are rare, they offer valuable insights into the mechanisms behind Alzheimer’s. Professor Jonathan Schott, co-author and Chief Medical Officer at Alzheimer’s Research UK, emphasized the importance of this research in advancing our understanding of Alzheimer’s. Dr. Gargi Banerjee, the study’s first author, reiterated that while amyloid-beta pathology can be transmitted through repeated exposure to contaminated material, this does not suggest Alzheimer’s can be acquired through close contact or everyday activities.

This discovery opens a new chapter in Alzheimer’s research, potentially leading to breakthroughs in treatment and prevention of the disease in the future.

By Impact Lab