Background: The aggregation of misfolded proteins in the brain occurs in several neurodegenerative disorders. Aberrant protein aggregation is inducible in rodents and primates by intracerebral inoculation. Possible transfusion transmission of neurodegenerative diseases has important public health implications.
Objective: To investigate possible transfusion transmission of neurodegenerative disorders.
Design: Retrospective cohort study.
Setting: Nationwide registers of transfusions in Sweden and Denmark.
Participants: 1 465 845 patients who received transfusions between 1968 and 2012.
Measurements: Multivariable Cox regression models were used to estimate hazard ratios for dementia of any type, Alzheimer disease, and Parkinson disease in patients receiving blood transfusions from donors who were later diagnosed with any of these diseases versus patients who received blood from healthy donors. Whether excess occurrence of neurodegenerative disease occurred among recipients of blood from a subset of donors was also investigated. As a positive control, transmission of chronic hepatitis before and after implementation of hepatitis C virus screening was assessed.
Results: Among included patients, 2.9% received a transfusion from a donor diagnosed with one of the studied neurodegenerative diseases. No evidence of transmission of any of these diseases was found, regardless of approach. The hazard ratio for dementia in recipients of blood from donors with dementia versus recipients of blood from healthy donors was 1.04 (95% CI, 0.99 to 1.09). Corresponding estimates for Alzheimer disease and Parkinson disease were 0.99 (CI, 0.85 to 1.15) and 0.94 (CI, 0.78 to 1.14), respectively. Hepatitis transmission was detected before but not after implementation of hepatitis C virus screening.
Limitation: Observational study design, underascertainment of the outcome, and possible insufficient statistical power.
Conclusion: The data provide no evidence for the transmission of neurodegenerative diseases and suggest that if transmission does occur, it is rare.
Primary funding source: Swedish Research Council, Swedish Heart-Lung Foundation, Swedish Society for Medical Research, and Danish Council for Independent Research.