Alzheimer’s is not contagious. However, recent research revealed that, in rare cases, the disease may have been transmitted indirectly to others. It occurred due to a no-longer-used medical treatment.
Alzheimer’s is a neurodegenerative disorder that impairs brain function and causes memory loss and confusion.
The condition’s precise cause is yet unknown. Numerous pieces of evidence, however, indicate that environmental, lifestyle, and genetic variables play a role. How these factors combine and contribute to Alzheimer’s development is the focus of various ongoing investigations.
Patients with Alzheimer’s disease usually have shrinking brain tissues. This occurs as a result of tangles forming due to the aberrant twisting of the “tau” protein strands. Additionally, the amyloid-beta peptides form plaques through irregular folding.
Both of these ultimately lead to the loss of synapses and the eventual death of brain cells. These cellular alterations are consistent with Alzheimer’s symptoms. Cognitive impairment, unreasonable behavior, trouble remembering daily routines or making decisions, and various other psychological changes are some of these symptoms.
Alzheimer’s and Transmissible Proteins
Alzheimer’s is commonly associated with several risk factors, including genetic mutations, age, gender, pollution, and specific foods. None of which suggests that an affected person could directly spread Alzheimer’s.
However, in 2015, a group of scientists contested this idea. They conducted a brain autopsy on eight people who had been injected with a growth hormone extracted from human cadavers [1].
Misfolded proteins known as “prions” inadvertently contaminated some of these products, leading to the deadly neurological disorder known as Creutzfeldt-Jakob disease. An older study had already reported that a childhood therapy with cadaver-derived human growth hormone contaminated more than 200 persons globally with CJD prions, resulting in iatrogenic Creutzfeldt-Jakob disease. “Iatrogenic” refers to a disorder that can occur as a result of a medical treatment [2].
Scientists noticed white plaques in these people’s brains in addition to prions. This finding raised the possibility that growth hormone injections could potentially have been a means of amyloid-beta protein transmission.
Additionally, the findings also suggested that amyloid-beta protein could unintentionally spread during brain surgery. However, these people’s brains lacked “tau” protein tangles, another hallmark of Alzheimer’s.
Similar evidence emerged between 1958 AD and 1985 when roughly 30,000 people worldwide got growth hormone injections to overcome short stature [1]. These products were similarly obtained from human cadavers infected with prions.
When the risk of Creutzfeldt-Jakob disease became apparent in a few patients, the scientists discontinued the administration. There have been theories that the amyloid-beta protein may spread like a virus (much like prions).
In a more recent study conducted in 2024, the researchers discovered that individuals who received this medication as children and subsequently passed away from iatrogenic Creutzfeldt-Jakob disease had amyloid-beta pathology. They demonstrated how injecting mice with the amyloid-beta peptide could spread the disease [3].
However, there is no proof that tau or amyloid-beta can spread from person to person in daily life.
More Studies
A study investigated the possibility of human-to-human transmission of Alzheimer’s. A significant characteristic of the disease is the accumulation of tau and beta-amyloid proteins in the brain [4].
Scientists discovered that injecting mice with human growth factor containing beta-amyloid and prions sped up the accumulation of amyloid plaques, especially in the brain’s blood vessels.
Researchers also showed that injecting mice with human Alzheimer’s brain tissue caused an accumulation of amyloid in the brain’s blood vessels. They also discovered, through mouse research, that amyloid in the blood can move to the brain and induce Alzheimer’s symptoms.
Other studies examined adolescents who had cadaveric hormone growth factor treatment for short stature and subsequently acquired Creutzfeldt-Jakob disease as a result of the treatment. Researchers discovered that most human growth factor vials included tau and beta-amyloid proteins.
The study participants did not accumulate tau proteins despite the presence of tau proteins in the human growth factor. It is unclear whether tau proteins are transmissible or if transmission may take longer to manifest in test results.
Researchers are investigating whether nonsterile surgical instruments and blood transfusions could transfer Alzheimer’s, as is the case with prion illnesses.
An analysis of 1,465,845 individuals examined the possibility of neurodegenerative diseases being transmitted through blood transfusions from donors who subsequently experienced these conditions [5].
Blood transfusions did not appear to raise Alzheimer’s risk. Additionally, there is no proof that surgical equipment can spread the disease.
According to the review’s findings, amyloid may spread from person to person similarly to prions, but further research is needed to determine whether this could cause Alzheimer’s.
Can Alzheimer’s Spread from Person to Person?
Given the available data, it is evident that Alzheimer’s is not transmissible despite its exact etiology being unknown. Intimate or general physical contact does not spread it.
However, research did indicate that there may have been a few rare cases in which the illness was indirectly transmitted to other people.
It did not spread in the same manner as a bacterial or viral infection. It resulted from an antiquated medical procedure.
Alzheimer’s Research Association is a non-profit organization dedicated to helping caregivers of Alzheimer’s disease and dementia. We provide the latest information and news about the illness and helpful tips to help caregivers cope with their daily caregiving challenges. We realize the most important thing that a caregiver needs is financial assistance. Therefore, we provide grants to caregivers to ease their financial burden. Caregivers can apply for grants here: Alzheimer’s Grant Application.
You can also help caregivers in their endeavor by donating as much as possible: Donation To Alzheimer’s Research Associations.
References
- Jaunmuktane, Z., Mead, S., Ellis, M., Wadsworth, J.D., Nicoll, A.J., Kenny, J., Launchbury, F., Linehan, J., Richard-Loendt, A., Walker, A.S. and Rudge, P., 2015. Evidence for human transmission of amyloid-β pathology and cerebral amyloid angiopathy. Nature, 525(7568), pp.247-250.
- Swerdlow, A.J., Higgins, C.D., Adlard, P., Jones, M.E. and Preece, M.A., 2003. Creutzfeldt-Jakob disease in United Kingdom patients treated with human pituitary growth hormone. Neurology, 61(6), pp.783-791.
- Banerjee, G., Farmer, S.F., Hyare, H., Jaunmuktane, Z., Mead, S., Ryan, N.S., Schott, J.M., Werring, D.J., Rudge, P. and Collinge, J., 2024. Iatrogenic Alzheimer’s disease in recipients of cadaveric pituitary-derived growth hormone. Nature Medicine, 30(2), pp.394-402.
- Bu, X.L., Li, W.W. and Wang, Y.J., 2019. Is Alzheimer’s disease transmissible in humans?. Neuroscience Bulletin, 35, pp.1113-1115.
- Edgren, G., Hjalgrim, H., Rostgaard, K., Lambert, P., Wikman, A., Norda, R., Titlestad, K.E., Erikstrup, C., Ullum, H., Melbye, M. and Busch, M.P., 2016. Transmission of neurodegenerative disorders through blood transfusion: a cohort study. Annals of internal medicine, 165(5), pp.316-324.
- Is Alzheimer’s Disease Transmissible? News Medical. https://www.news-medical.net/health/Is-Alzheimers-Disease-Transmissible.aspx. Updated Online: 28th June, 2019. Accessed: 6th January, 2025.
- Wigley, S. Is Alzheimer’s Contagious? Healthline. https://www.healthline.com/health/is-alzheimers-contagious. Published Online: 18th December, 2024. Accessed: 6th January, 2025.
- Sissons, B. Is Alzheimer’s disease contagious? Medical News Daily. https://www.medicalnewstoday.com/articles/is-alzheimers-contagious. Updated Online: 24th September, 2023. Accessed: 6th January, 2025.