Potential Blood-Borne Transmission of Alzheimer’s Pathology

Scientists reviewing evidence in *The Lancet* argue that amyloid-beta proteins linked to Alzheimer’s disease could be conveyed through blood transfusions. The hypothesis builds on a series of studies suggesting that pathological protein “seeds” may move between patients during medical procedures.

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Alzheimer’s has traditionally been viewed as a sporadic disorder shaped by age, genetics and lifestyle. Recent research proposes an infection-like mechanism, likening amyloid-beta spread to prion diseases. Early work in 2015 provided the first real-world indication that amyloid pathology might transfer between humans, with follow-up studies in 2016 reinforcing the possibility. A 2018 paper extended the idea to contaminated surgical tools, proposing that misfolded proteins could induce pathology in otherwise healthy tissue.

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• 2015–2016 studies reported transferable amyloid markers in medical settings.

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• 2018 research suggested surgical instruments could act as vectors for amyloid-beta.

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• 2023 Scandinavian population analysis of Denmark and Sweden, encompassing over 1 million individuals, found that recipients of blood from donors who later suffered intracerebral hemorrhages showed a higher incidence of subsequent brain bleeds—a hallmark of cerebral amyloid angiopathy (CAA), a condition associated with amyloid-beta.

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• 2024 UK Infected Blood Inquiry examined a historic blood-contamination scandal affecting more than 30,000 patients, underscoring the risks of delayed safety actions.

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He notes that the most plausible explanation for the Scandinavian findings is the transfer of incipient amyloid-beta seeds present in donor blood. Collinge also cites the UK Infected Blood Inquiry as a cautionary example, urging proactive transparency about possible amyloid-beta transmission.

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She calls for large-scale epidemiological studies and the development of blood-based biomarkers to pinpoint donors who might carry amyloid-beta pathology, while acknowledging that current risks appear theoretical.

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• “The Infected Blood Inquiry provides a cautionary tale in waiting for absolute certainty before making decisions on patient safety,” — John Collinge

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• “What this review does is identify an important gap in our knowledge,” — Susan Kohlhaas, Executive Director of Research and Partnerships at Alzheimer's Research UK

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