Alzheimer’s disease can spread between people, according to a groundbreaking study.
Experts have found evidence that at least five people ‘contracted’ the memory-robbing disorder from now-banned hormone treatments.
The patients were among 1,848 people who were injected as children with growth hormones seeded with toxic “seeds” of amyloid beta protein, or prions.
All five suffered from the same rare early form of the devastating dementia.
Others who received the same treatment are now considered ‘high risk’.
Between 1958 and 1985, abnormally small children in the US and Britain were given hormones from cadavers to stimulate their growth.
The technique was subsequently banned and doctors used synthetic hormones instead after some batches were found to be contaminated with prions, leading to a fatal and incurable brain disease, Creutzfeldt-Jakob disease (CJD).
Academics now believe that other medical and surgical procedures may pose a risk of spreading Alzheimer’s disease because prions – which build up in the brain and kill neurons – can survive sterilization methods in hospitals.
Five patients were among 1,848 injected as children with growth hormones infected with toxic ‘seeds’ of amyloid beta protein. All five suffered from the same rare early form of the devastating dementia. Others who received the same treatment are now considered ‘high risk’
But they can also be a sign of dementia – the memory-robbing disorder that affects almost 1 million Britons and 7 million Americans
Professor John Collinge from University College London said action must be taken to prevent accidental transmission in the future.
He said: ‘These patients received specific and long-discontinued medical treatment, which involved injecting them with material now known to be contaminated with disease-related proteins.
‘We now plan to look at ways to destroy prions from surgical equipment as they can withstand normal decontamination methods.’
Alzheimer’s disease was previously thought to come in two forms: a ‘sporadic’ variant affecting thousands of people over the age of 65, which is by far the most common, and a genetic, early-onset disease that runs in families.
The UCL scientists say they have now identified a third variant, which is slightly different from the others and very rare, and which can be passed 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 caused the production of Alzheimer’s-causing proteins.
However, Professor Collinge said the risk group is extremely small, consisting of patients who have undergone certain neurosurgical procedures, tissue transplantation or organ donation.
He said: ‘There is a risk group. Those given the infected growth hormone were all told many years ago that they were at risk of developing CJD.
‘There is now a possible risk that they will develop Alzheimer’s disease. But these risks cannot currently be quantified.’
Researchers are currently following patients to study what happens in their brains and detect any problems early.
Professor Collinge added: ‘I must emphasize that these are very rare events. You cannot “catch” Alzheimer’s disease, it is not transmissible in the sense of a viral or bacterial infection.
‘These rare transmission routes have involved people being accidentally injected 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 point researchers in the right direction to understand and treat 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 thoughts go out to the families affected by these tragic circumstances.
‘It is important to emphasize that this is the only recorded 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 possible new targets for tomorrow’s treatments.
“We will continue to redouble our research efforts in our pursuit of a cure.”
The people described in the study had all been treated as children with a type of human growth hormone derived from dead donors (cadaver-derived human growth hormone, or c-hGH).
But the treatment was stopped in 1985 after the link with CJD came to light.
Afterwards, c-hGH was replaced by a synthetic growth hormone that did not pose a risk of transmitting CJD.
Around 900,000 Britons currently suffer from dementia, with Alzheimer’s disease being the most common form.