Recent research published in The Lancet has re-examined the possibility that Alzheimer's disease might be transmitted through blood transfusions. Scientists have looked at several studies over the past decade, including a 2015 study that first suggested amyloid pathology—characteristic of Alzheimer's—could be passed between humans via medical procedures. A 2016 study added more evidence to this idea, and research from 2018 suggested that contaminated surgical instruments might spread Alzheimer's-related proteins between patients. Most recently, a 2023 study of a large group of people in Denmark and Sweden found that individuals who received blood from donors who later developed brain bleeds were more likely to experience similar issues years later. Spontaneous cerebral hemorrhages—unexplained bleeding in the brain—are a symptom of cerebral amyloid angiopathy (CAA), a condition where abnormal beta-amyloid proteins build up in blood vessels in the brain. While CAA is different from Alzheimer's disease, both involve the same type of protein. John Collinge, a neurologist at University College London and co-author of the report, proposed that beta-amyloid "seeds" in a donor's blood might be transferred during a transfusion, potentially triggering similar issues in the recipient. The researchers emphasize that while the studies do not prove Alzheimer's can be transmitted through blood, the evidence is strong enough to consider protective measures. They suggest conducting large-scale studies to see if other substances, besides beta-amyloid, might be passed through transfusions. They also recommend more careful monitoring of patients who need frequent transfusions and developing ways to detect beta-amyloid in blood donors using biomarkers. These steps could help prevent the spread of the protein if it is indeed transmissible. Collinge referenced the infamous blood scandal of the 1980s and 1990s, when thousands of patients were infected with HIV or hepatitis C through contaminated blood transfusions. He stressed the importance of being transparent about potential risks to address them early. The researchers concluded that the possibility of beta-amyloid being transmitted through blood transfusions is a valid concern that warrants further investigation and precaution.