Previous studies have shown that neurological diseases such as Alzheimer's and Parkinson's can be induced in healthy laboratory animals, causing concern that dementia diseases can be transmitted between individuals, possibly via blood transfusions. However, in a new study published in The Annals of Internal Medicine, a team from Karolinska Institutet shows that the diseases are not transmitted.
Studies published in recent years have shown that a number of neurological conditions can be induced in healthy laboratory animals through the injection of diseased brain tissue from human sufferers. To determine whether dementia diseases can be transmitted between people via blood transfusion, researchers at Karolinska Institutet conducted a study based on a unique Swedish-Danish transfusion database. Their results demonstrate that dementia diseases are not transmitted in this way.
"The results are unusually clear for such a complicated subject as this," says principal investigator Gustaf Edgren, docent at the Department of Medical Epidemiology and Biostatistics. "We've been working with this question for a long time now and have found no indication that these diseases can be transmitted via transfusions."
The study was a collaboration with researchers at Statens Serum Institut in Copenhagen and was carried out using data on a total of 1.7 million blood donors and 2.1 million patients given blood transfusions in Sweden and Denmark. The researchers were able to identify over 40,000 patients who had been given blood from donors diagnosed with one of the studied dementia diseases within 20 years of having given blood.
The patients were then followed up for a maximum of 44 years through the linking of a number of registries, including the Swedish and Danish patient registries. A total of 1.4 million patients who had not received blood from donors with a subsequent diagnosis were used as controls. The two groups were compared through statistical analysis taking account of sex, age, place of residence, blood group, number of transfusions and time since first transfusion. It turned out that the patients in the two groups had exactly the same risk of contracting these dementia diseases.
"Blood transfusions are extremely safe in the Western world today, but even so we are working continuously and proactively on identifying any overlooked risks," says Dr Edgren. "The Swedish-Danish database that we have built up and used in many similar studies clearly demonstrates the value of our vast health registries. This kind of study would have simply been extremely difficult anywhere else in the world."
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