A review published in The Lancet has assessed the existing evidence for whether amyloid-beta proteins associated with Alzheimer’s disease could potentially be transmitted between individuals through blood transfusions, concluding that the concern is scientifically plausible and warrants further investigation, while stopping short of confirming that transmission is occurring.
The hypothesis that Alzheimer’s-related pathology may spread via medical procedures has been building since 2015, when a study provided the first real-world indication that amyloid pathology might be transferable between humans. A key development came in 2023, when a large population study involving over one million individuals in Denmark and Sweden found that recipients of blood from donors who later developed intracerebral haemorrhage were themselves more likely to develop recurrent brain bleeds years afterwards. Spontaneous cerebral bleeding is a characteristic feature of cerebral amyloid angiopathy (CAA), a condition distinct from Alzheimer’s disease but also associated with amyloid-beta accumulation. The review authors describe transmission of pre-symptomatic amyloid-beta seeds via donated blood as the most biologically plausible explanation for this pattern, though they acknowledge the evidence remains circumstantial.
The authors, led by neurologist John Collinge of University College London, call for large-scale epidemiological studies modelled on the Scandinavian research, enhanced monitoring of patients requiring repeated transfusions, and development of blood biomarker screening systems to identify donors potentially carrying amyloid-beta pathology. They draw an explicit parallel with the UK infected blood scandal, in which more than 30,000 patients may have received contaminated blood between the 1970s and 1990s, citing it as a cautionary example of the risks of delaying precautionary action pending absolute certainty.
Experts not involved in the review concur that current evidence is insufficient to quantify the risk but support prioritising research to address the knowledge gap.
Source: Dockrill P. Can Alzheimer’s Spread Through Blood Transfusions? ScienceAlert, 25 August 2026. Primary review published in The Lancet.
