Groundbreaking study reveals that Alzheimer's Disease can be transmitted between people
In a groundbreaking discovery, scientists have presented the first evidence of Alzheimer's disease transmission in living individuals. (CREDIT: Creative Commons)
In a groundbreaking discovery, scientists have presented the first evidence of Alzheimer's disease transmission in living individuals. A recent paper published in Nature Medicine sheds light on a remarkable case where Alzheimer's appears to have been medically acquired through the transmission of the amyloid-beta protein.
Typically considered a sporadic condition of late adult life or an inherited condition resulting from faulty genes, Alzheimer's disease has long remained a complex puzzle for researchers. However, this new study brings to the forefront a unique scenario, where the disease was seemingly transmitted through medical treatment.
The individuals in question had all received a type of human growth hormone known as cadaver-derived human growth hormone (c-hGH) during their childhood. This hormone was derived from pituitary glands harvested from deceased individuals and was employed to treat various causes of short stature. Remarkably, c-hGH was administered to at least 1,848 people in the UK between 1959 and 1985.
Magnetic resonance and amyloid-PET (18F-Florbetapen) images—case 3. High-resolution three-dimensional (3D) T1-weighted (T1W) magnetic resonance (MR) coronal image through the temporal lobes demonstrates volume loss within the temporal lobes bilaterally (arrows) and also marked central atrophy. (CREDIT: Nature Medicine)
Unfortunately, c-hGH was withdrawn from use in 1985 due to the realization that some batches were contaminated with prions, infectious proteins known to cause Creutzfeldt-Jakob disease (CJD). Consequently, synthetic growth hormone, devoid of the risk of transmitting CJD, replaced c-hGH in medical practice.
Previous research by these scientists had already established a link between c-hGH treatment and the premature development of amyloid-beta protein deposits in the brains of some patients diagnosed with iatrogenic CJD.
Furthermore, in a 2018 study, they demonstrated that archived samples of c-hGH were indeed contaminated with amyloid-beta protein and could transmit amyloid-beta pathology to laboratory mice when injected.
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Building upon these findings, the researchers hypothesized that individuals exposed to contaminated c-hGH who did not succumb to CJD might eventually develop Alzheimer's disease.
This latest paper details the cases of eight individuals who had received c-hGH treatment during their childhood, often spanning several years. Five of these individuals exhibited symptoms of dementia, either with a confirmed Alzheimer's diagnosis or meeting the diagnostic criteria for the disease. The onset of neurological symptoms occurred surprisingly early, with the patients ranging in age from 38 to 55 when they first experienced symptoms.
Biomarker analyses further supported the diagnoses of Alzheimer's disease in two patients and hinted at Alzheimer's in another individual. An autopsy analysis confirmed Alzheimer's pathology in yet another patient. The unusually young age at which these patients developed symptoms strongly suggests that this was not the typical late-onset sporadic Alzheimer's.
Brain biopsy—case 2. Images shown are from a left frontal lobe brain biopsy. (CREDIT: Nature Medicine)
Genetic testing ruled out inherited Alzheimer's disease in the five patients who provided samples. Since c-hGH treatment is no longer in use, there is no risk of new transmissions through this method. Moreover, there have been no reported cases of Alzheimer's disease acquired through any other medical or surgical procedures, nor any indication that amyloid-beta can be transmitted during routine medical or social care.
However, the researchers emphasize the importance of reviewing safety measures to prevent the accidental transmission of amyloid-beta through other medical or surgical procedures that have previously been linked to CJD transmission.
Postmortem brain tissue—case 1. Immunostaining for Aβ shows frequent parenchymal deposits in the cortex (a and c) and caudate nucleus (b), with rare, isolated deposits in the cerebellar cortex (d, pink arrowhead). (CREDIT: Nature Medicine)
Professor John Collinge, the lead author of the research and Director of the UCL Institute of Prion Diseases, clarified, "There is no suggestion whatsoever that Alzheimer's disease can be transmitted between individuals during activities of daily life or routine medical care." He added that these cases were linked to a specific and discontinued medical treatment involving contaminated materials.
Professor Jonathan Schott, a co-author and Chief Medical Officer at Alzheimer's Research UK, echoed the sentiment that while these cases are highly unusual, they offer valuable insights into disease mechanisms that could be instrumental in understanding and treating Alzheimer's disease in the future.
Post-mortem brain tissue, Case 2. Haematoxylin and eosin-stained preparation demonstrates extensively calcified and ossified adamantinomatous craniopharyngioma invading into the brain tissue, without any histological signs of malignant transformation. (CREDIT: Nature Medicine)
Dr. Gargi Banerjee, the first author of the study, highlighted, "We have found that it is possible for amyloid-beta pathology to be transmitted and contribute to the development of Alzheimer's disease." However, she emphasized that this transmission occurred only after repeated treatments with contaminated material, reiterating that Alzheimer's disease cannot be acquired through close contact or routine care provision.
The discovery of Alzheimer's transmission through c-hGH treatment underscores the intricate nature of this debilitating disease, paving the way for further research and a deeper understanding of its causes and potential treatment strategies.
Who has Alzheimer’s Disease?
In 2020, as many as 5.8 million Americans were living with Alzheimer’s disease.
Younger people may get Alzheimer’s disease, but it is less common.
The number of people living with the disease doubles every 5 years beyond age 65.
This number is projected to nearly triple to 14 million people by 2060.
Symptoms of the disease can first appear after age 60, and the risk increases with age.
What is known about Alzheimer’s Disease?
Scientists do not yet fully understand what causes Alzheimer’s disease. There likely is not a single cause but rather several factors that can affect each person differently.
Age is the best known risk factor for Alzheimer’s disease.
Family history—researchers believe that genetics may play a role in developing Alzheimer’s disease. However, genes do not equal destiny. A healthy lifestyle may help reduce your risk of developing Alzheimer’s disease. Two large, long term studies indicate that adequate physical activity, a nutritious diet, limited alcohol consumption, and not smoking may help people.
Changes in the brain can begin years before the first symptoms appear.
Researchers are studying whether education, diet, and environment play a role in developing Alzheimer’s disease.
There is growing scientific evidence that healthy behaviors, which have been shown to prevent cancer, diabetes, and heart disease, may also reduce risk for subjective cognitive decline.
What is the burden of Alzheimer’s disease in the United States?
Alzheimer’s disease is one of the top 10 leading causes of death in the United States.
The 6th leading cause of death among US adults.
The 5th leading cause of death among adults aged 65 years or older.
In 2020, an estimated 5.8 million Americans aged 65 years or older had Alzheimer’s disease. This number is projected to nearly triple to 14 million people by 2060.
In 2010, the costs of treating Alzheimer’s disease were projected to fall between $159 and $215 billion. By 2040, these costs are projected to jump to between $379 and more than $500 billion annually.
Death rates for Alzheimer’s disease are increasing, unlike heart disease and cancer death rates that are on the decline.
Dementia, including Alzheimer’s disease, has been shown to be under-reported in death certificates and therefore the proportion of older people who die from Alzheimer’s may be considerably higher.
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