Alzheimer's disease can be transmitted between people, a groundbreaking study revealed today.
Experts have found evidence that at least five people “infected” the memory-robbing disorder through now-banned hormone treatments.
The patients were among 1,848 people who were injected as children with growth hormone laced with toxic amyloid beta protein “seeds,” or prions.
All five suffered from the same rare, early-onset form of the devastating dementia.
Others who received the same treatment are now considered “at risk.”
Between 1958 and 1985, unusually young children in Britain and the United States were given hormones extracted from cadavers to stimulate their growth.
The technique was then banned and doctors used synthetic hormones instead after some batches were found to be contaminated with prions, which led to a fatal and incurable brain disease called Creutzfeldt-Jakob disease (CJD). CJD itself is closely linked to mad cow disease.
Scientists now believe that other medical and surgical procedures could pose a risk of spreading Alzheimer's because prions – which accumulate in the brain and kill neurons – can survive hospital sterilization methods.
Five of the 1,848 patients injected with growth hormone were infected with toxic amyloid beta protein “seeds” as children. All five suffered from the same rare, early-onset form of the devastating dementia. Others who received the same treatment are now considered “at risk.”
As prions build up in the brain, plaque buildup can occur in the brain, according to the NHS. Abnormal protein buildups in and around neurons are believed to be the cause of Alzheimer's disease.
Professor John Collinge, from University College London, said measures need to be taken to prevent accidental transmission in the future.
He said: “These patients received a specific and long-discontinued medical treatment in which they were injected with material now known to be contaminated with disease-related proteins.”
“We now plan to look for ways to destroy prions from surgical devices because they can resist normal decontamination methods.”
Scientists develop blood test for Alzheimer's disease
A pinprick blood test has been developed to determine the likelihood of developing dementia in the future.
The home testing kit, developed by charity FoodfortheBrain.org, measures blood sugar, vitamin D, omega-3 and B vitamin status as potentially modifiable risks for dementia.
People then receive a risk assessment and dietary tips to reduce it as part of a global prevention study.
The charity hopes to enroll one million people worldwide, making it the largest global citizen science prevention initiative.
Founder Patrick Holford said: “Alzheimer’s is a preventable but not reversible disease.” Less than one in a hundred cases is directly genetic.
“Prevention is certainly possible if you identify early enough who is at risk and encourage the right diet and lifestyle changes.”
Higher levels of omega-3 fatty acids from foods like fatty fish and the sunshine vitamin vitamin D are also associated with a lower risk of disease.
Participants will be asked to complete an online cognitive function test before being sent the Dementia Risk Index Functional Test, which they can complete at home and which measures the strength of each risk factor. Both test results are then analyzed and tracked over time.
It was previously thought that there were two forms of Alzheimer's: a “sporadic” variant that affects thousands of people over 65 and is by far the most common, and a genetic, early-onset form that runs in families.
The UCL scientists say they have now identified a third variant, which is slightly different to the others and is very rare and can be transmitted from one person to another.
Batches of the infected growth hormone were stored as dried powder in a Ministry of Health archive.
UCL scientists were allowed to test the decades-old powder on mice and found that it triggered the production of Alzheimer's-causing proteins.
However, Professor Collinge said the group at risk was extremely small – consisting of patients who had undergone certain neurosurgical procedures, tissue transplants or organ donations.
He said: “There is a risk group out there.” Those given the infected growth hormone were all informed many years ago that they were at risk of developing CJD.
“There is now a possible risk that they will develop Alzheimer's disease. However, these risks cannot currently be quantified.”
Researchers are currently monitoring patients to study what is happening in their brains and detect any problems early.
Professor Collinge added: “I would like to emphasize that these are very rare occurrences.” You cannot “catch” Alzheimer's, it is not transmissible in the sense of a viral or bacterial infection.
“These rare routes of transmission have involved inadvertently injecting people with infected human tissue extracts, and the majority of these involve medical procedures that are no longer used.”
“From a public health perspective, this is likely to affect a relatively small number of patients.”
He added that the new findings could help researchers point in the right direction for understanding and treating Alzheimer's disease in the future.
Dr. Susan Kohlhaas, executive director of research at Alzheimer's Research UK, said: “A diagnosis of Alzheimer's disease can be devastating for everyone involved and our condolences go out to the families affected by these tragic circumstances.”
But they can also be a sign of dementia – the memory-robbing disease that affects almost a million Brits and seven million Americans
“It is important to emphasize that this is the only documented case of Alzheimer's transmission between humans.”
“However, this study has revealed more about how amyloid fragments can spread in the brain, providing further clues about the progression of Alzheimer's disease and potential new targets for tomorrow's treatments.”
“We will continue to redouble our research efforts in the search for a cure.”
The people described in the study had all been treated as children with a type of human growth hormone obtained from dead donors (cadaver-derived human growth hormone, or c-hGH).
However, treatment was discontinued in 1985 after the link between CJD and CJD became known.
c-hGH was then replaced with a synthetic growth hormone that poses no risk of CJD transmission.
Human-donated growth hormone has been produced in different ways. All batches made using a method called HWP were infected with toxic prions, the experts found.
Theoretically, one dose of HWP could be enough to infect a patient with Alzheimer's seeds, but it is unknown how many actually received the HWP variant.
Most patients received different types of preparations during their treatment.
Around 900,000 Brits are currently living with dementia, with Alzheimer's being the most common form.
What is Alzheimer's and how is it treated?
Alzheimer's disease is a progressive, degenerative brain disease in which the buildup of abnormal proteins causes nerve cells to die.
This disrupts the transmitters carrying messages and causes the brain to shrink.
More than 5 million people suffer from the disease in the US, where it is the sixth leading cause of death, and it affects more than 1 million Britons.
WHAT HAPPENS?
When brain cells die, the functions they provide are lost.
These include memory, orientation and the ability to think and reason.
The course of the disease is slow and insidious.
On average, patients live five to seven years after diagnosis, although some live 10 to 15 years.
EARLY SYMPTOMS:
- Loss of short-term memory
- Disorientation
- Behavioral changes
- Mood swings
- Difficulty handling money or making phone calls
LATER SYMPTOMS:
- Severe memory loss, forgetting close family members, familiar objects or places
- Fear and frustration over the inability to understand the world, leading to aggressive behavior
- Eventually loses the ability to walk
- May have problems eating
- The majority will require 24-hour care at some point
HOW IS IT TREATED?
There is no known cure for Alzheimer's disease.
However, there are some treatments available that may help relieve some of the symptoms.
One of these are acetylcholinesterase inhibitors, which help brain cells communicate with each other.
Another drug is menantine, which blocks a chemical called glutamate, which can build up in the brains of people with Alzheimer's disease and inhibit mental function.
As the disease progresses, Alzheimer's patients may exhibit aggressive behavior and/or suffer from depression. Medication may be given to relieve these symptoms.
Other non-pharmaceutical treatments such as mental training to improve memory, which help combat this one aspect of Alzheimer's disease, are also recommended.
Source: Alzheimer's Association and NHS