Alzheimer's disease has long been considered a condition resulting from multiple factors such as age, genetics, and lifestyle, but researchers are now questioning whether this is the only way the disease develops.
In recent years, studies have suggested that Alzheimer's may be transmitted through infection, perhaps in a manner similar to the transmission of pathogens, prompting a team of scientists to review the evidence on the possibility of the disease-associated beta-amyloid proteins being transmitted through blood transfusions, in a new report published in The Lancet.
John Collinge, a neurologist at University College London, said: "Blood transfusions are lifesaving, but to ensure maximum safety, any potential risks must be thoroughly investigated."
These concerns have their roots in 2015, when a study provided the first real-world evidence that amyloid diseases could be transmitted between humans via medical procedures, followed by studies in 2016 and 2018 that revealed additional evidence, including the possibility of proteins being transmitted via contaminated surgical instruments.
In 2023, a significant turning point came with a large population-based study from Denmark and Sweden involving over one million people. This study found that individuals who received blood transfusions from donors who later suffered intracerebral hemorrhages were more likely to experience recurrent cerebral hemorrhages years later. This finding is important because spontaneous cerebral hemorrhage is a hallmark symptom of cerebral amyloid angiopathy (CAA), a condition linked to the same beta-amyloid proteins associated with Alzheimer's disease.
Researchers believe the most plausible explanation is that early seeds of beta-amyloid proteins were present in the blood of donors and were transferred to recipients during blood transfusions, without necessarily developing into cerebral amyloid angiopathy. However, they acknowledge that this is merely a hypothesis requiring further investigation.
However, the team calls for preventative measures, including conducting large-scale epidemiological analyses, monitoring patients at higher risk, and developing a system for screening donors using Alzheimer's biomarkers.
Researchers cite the contaminated blood scandal in Britain (uncovered by the 2024 inquiry and affecting more than 30,000 patients between the 1970s and 1990s) as a warning against the dangers of waiting for absolute certainty before making patient safety decisions.
Although experts stress that the currently known risks are small, they call for more research to determine whether blood-borne transmission actually occurs, who is most at risk, and whether preventive measures are needed.
