Is Alzheimer's Disease Infectious? Can I Catch It?

Hugging a Loved One with Alzheimer's
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Does Alzheimer's Disease Have Germs Like the Common Cold?

Ever wonder if you can "get" Alzheimer's disease from spending time with people who have it?

Rest assured, holding your grandmother's hand or giving her a hug will not give you Alzheimer's disease. Nor will taking a job as a certified nursing assistant at a nursing home and spending daily time dressing, bathing and caring for people in a secure dementia unit.

Research about How Alzheimer's Disease Spreads

While Alzheimer's disease is not spread through contact with others, some research with mice seems to indicate that it could have some type of an infectious component, possibly related to prions (proteins that brain cells need to function). In prion diseases, including Creutzfeldt-Jakob disease, prion proteins begin to fold abnormally and then infect other healthy prions they encounter within the body, causing cells to die in the brain and dementia to develop. Although the unhealthy prions spread within a person, there is virtually no risk of the disease affecting other people around that individual, including family members or those caring for that person.

  • Studies with Mice

Scientists conducted research with mice, taking healthy mice and injecting them with the beta amyloid protein from the brains of mice who had been engineered to develop Alzheimer's disease and displayed memory loss.

Researchers found that the mice who had received the injection eventually developed the same protein build-up in their brains and the memory loss that the mice with Alzheimer's already had.

The researchers then tried administering the infected proteins by way of the mouth, eyes, and nose, as well as intravenously, in healthy mice and found that these mice did not develop symptoms of Alzheimer's disease.

A second similar study found that healthy mice also developed the equivalent of Alzheimer's when their brains were injected with brain tissue from human Alzheimer's patients.

  • Retrospective Study with Humans

One retrospective study (a study that compares persons exposed to a specific factor to those who were not) consisted of following up on more than 6,100 people who had been previously injected with human growth hormones. The researchers tested those hormones and found that (unknowingly at the time), they contained small amounts of the tau and beta amyloid proteins that are present in the brains of people who have Alzheimer's. These people have since been monitored to determine if they have developed Alzheimer's disease. Thus far, none of the participants have developed Alzheimer's disease, although most are still fairly young for a typical onset of dementia.

Can Stainless Steel Instruments Spread Alzheimer's Disease?

In one of the studies with mice described above, researchers coated stainless steel wires with small amounts of the Alzheimer's-infected proteins and implanted them in the brains of healthy mice.

They discovered that these mice later developed Alzheimer's disease, but only if the wires had been boiled before implantation instead of being plasma sterilized, a highly effective method of sterilization.

Researchers investigated this possibility because previous studies have shown that Creutzfeldt-Jakob disease, a neurological disorder that is sometimes mistakenly called "mad cow disease," can be spread from one patient to the next through the use of surgical instruments that were not fully sterilized, as well as through other means.

Is There a Risk of Being Infected with Alzheimer's Disease?

Science is still working on determining what really causes Alzheimer's disease. We know that risk factors like age, genetics, family history and lifestyle are all part of the picture. It's also possible that an infectious property such as prions may be involved in Alzheimer's disease, but this potential is unproven at this time and is based only on preliminary research with mice.

If it turns out that prions do play a role in Alzheimer's disease, it's important to remember that prion diseases are not spread through casual or even intimate physical contact with others. So, go ahead and hug that person with Alzheimer's. Their disease is not contagious in any way, and they could experience some of the benefits related to appropriate physical touch for people with dementia, including lowering blood pressure, reducing pain and reducing challenging behaviors in dementia.


JAMA Neurology. 2013 Apr;70(4):462-8. Evaluation of potential infectivity of Alzheimer and Parkinson disease proteins in recipients of cadaver-derived human growth hormone.

Journal of Neuroscience.15 May 2000, 20(10):3606-3611. Evidence for Seeding of β-Amyloid by Intracerebral Infusion of Alzheimer Brain Extracts in β-Amyloid Precursor Protein-Transgenic Mice.

Molecular Psychiatry 17, 1347-1353 (December 2012) | doi:10.1038/mp.2011.120. De novo induction of amyloid-β deposition in vivo.

Proceedings of the National Academy of Sciences of the United States of America. August 4, 2009.106 (31). Induction of cerebral β-amyloidosis: Intracerebral versus systemic Aβ inoculation.

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