Published: 12-09-2023 17:00 | Updated: 13-09-2023 12:14

Risk of brain haemorrhage appears transmissible via blood transfusion

Blood transfusion.
Photo: Getty Images.

A major study published in JAMA led by researchers at Karolinska Institutet suggests that a possible cause of spontaneous brain haemorrhage could be transmitted via blood transfusion. At the same time, it is very unlikely that anyone should suffer a brain haemorrhage after receiving donated blood.

A common cause of spontaneous, recurring brain haemorrhages is the vascular disease cerebral amyloid angiopathy (CAA), in which proteins accumulate along the tiny blood vessels of the brain. Several studies have shown that CAA can be transferred from one individual to another through neurosurgery and probably via treatment using a certain type of growth hormone.

Few affected individuals

A new study by researchers from Karolinska Institutet, Södersjukhuset, Karolinska University Hospital in Sweden, the University of Copenhagen in Denmark, KU Leuven in Belgium and other institutions shows that patients who have received blood from donors who later suffered recurring brain haemorrhages are more than twice as likely to suffer a brain haemorrhage themselves.

Portrait of Cecilia Odlind and Gustaf Edgren. Photo: Andreas Andersson.
Gustaf Edgren. Photo: Andreas Andersson

The findings suggest that some factor that can give rise to spontaneous brain haemorrhages can be spread through blood transfusion. However, as only 0.1 per cent of the donors in the study subsequently suffered recurring brain haemorrhages there were consequently only a few affected patients.

“Blood transfusions are relatively common, which makes possible negative effects an important public health issue,” says the study’s last author Gustaf Edgren, researcher at the Department of Medicine, Karolinska Institutet (Solna) and specialist physician at Södersjukhuset. “However, in this case, it’s very unlikely that you’d suffer a brain haemorrhage from something transmitted through a transfusion.”

CAA could be transmissible

According to the researchers, the most important implication of the study is instead that it adds further support to the hypothesis that CAA can be transmitted between individuals, which, if true, can have consequences in several fields.

The study drew on the Swedish-Danish transfusion database SCANDAT, which contains data on blood donors and patients receiving a transfusion from the 1970s onwards. A total of more than a million patients were included. The primary analyses were conducted in Sweden and then repeated with the Danish data, with almost identical results.

The researchers now hope to corroborate the hypothesis that the link between brain haemorrhage and blood transfusion concerns CAA. They will therefore be examining samples from the Danish Blood Donor Study biobank to see if they can identify aberrant proteins associated with the disease.

Confirmation needed

The plan is also to obtain CAT and MR scans from the affected donors and patients to see if they might also be able to support the hypothesis.

Jingcheng Zhao
Jingcheng Zhao. Photo: Private

“This study does not demonstrate causality, so the observed increase in risk could depend on other factors,” says the study’s first author Jingcheng Zhao from Dr Edgren’s group at Karolinska Institutet. “More research is needed to confirm our findings and understand the potential underlying mechanism.”

The study was mainly financed by the Swedish Research Council and Region Stockholm (ALF funding). The researchers from KI report no commercial interests (see the paper for a full list of potential conflicts of interest).


Intracerebral hemorrhage among blood donors and their transfusion recipients”. Jingcheng Zhao, Klaus Rostgaard, Elsa Lauwers, Torsten Dahlén, Sisse Rye Ostrowski, Christian Erikstrup, Ole Birger Pedersen, Bart De Strooper, Robin Lemmens, Henrik Hjalgrim, Gustaf Edgren. JAMA (Journal of the American Medical Association), online 12 September 2023, doi: 10.1001/jama.2023.14445.

Editorial that comments on the results: "Blood Transfusion and Brain AmyloidosisShould We Be Worried?", Steven M. Greenberg, JAMA, online 12 September 2023, doi: 10.1001/jama.2023.14522.