New research has found that Alzheimer's could be transmitted between people
Experts said the toxic hallmark of the incurable illness could be transmitted between people, and have called for a review.
World-first studies show the seeds of Alzheimer’s could potentially attach to surgical instruments during medical procedures.
It provides the first evidence that the calling card of dementia could be transferred this way.
The new alert comes after amyloid proteins - which are central to the development of Alzheimer’s - were found in the brains of those who caught Mad Cow Disease from human growth hormones contaminated with infectious rogue proteins known as prions, which trigger chain reactions in the brain.
Bombshell British research suggests amyloid “seeds” could be passed through blood transfusions, dental work or contaminated surgical instruments in the same way.
The findings have prompted experts to call for an urgent review after evidence showed neurodegenerative diseases, including Alzheimer’s, might be “acquired”.
Professor John Collinge, who carried out the research, said: “You could have three different ways you have these protein seeds generated in your brain.
“Either they happen spontaneously, an unlucky event as you age, or you have got a faulty gene, or you’ve been exposed to a medical accident. That’s what we’re hypothesising.”
A study funded by the UK Medical Research Council and National Institute of Health Research now suggests amyloid protein fragments can stick to metal surfaces and resist conventional sterilisation.
It comes after scientists studied the autopsy files, including extensive brain tissue sampling, of eight Britons aged 36–51 with Creutzfeldt-Jakob Disease (CJD).
Each contracted the rare and fatal condition following treatment with prion-contaminated human growth hormone.
Professor John Collinge
Either they happen spontaneously, an unlucky event as you age, or you have got a faulty gene, or you’ve been exposed to a medical accident
Human transmission of prion disease has incubation periods that can exceed five decades.
Seven of the brains examined were found to have sticky amyloid deposits, a distinctive feature of those with Alzheimer’s.
Its presence can occur with natural ageing and does not mean they would have gone on to develop the disease, but experts said it was unusual to see such high levels in the brains of people aged 36 to 51. The fact each was a growth hormone recipient cannot be a coincidence, they said.
Growth hormone was harvested from pituitary glands of dead donors so recipients were exposed to brain material from large numbers of people, many of whom would have been elderly.
In the UK 1,848 people had the treatment, which started in 1958, some of which were inadvertently prion-contaminated. The practice stopped in 1985 following the link to CJD.
By 2012, 450 cases of CJD were identified worldwide after hormone treatment and other medical procedures, including transplant and neurosurgery.
Prof Collinge said: “The proteopathic seeds will potentially stick to metal surfaces, whatever the instrument is, the question is whether the instrument will have been exposed to those seeds. “Certainly, there are potential risks of dentistry where it’s impacting on nervous tissue, for example root canal treatment, and special precautions are taken with reamers that are used in root canal treatment for that reason.”
He added: “If you are speculating amyloid seeds might be transferred by instruments, one would have to consider whether certain types of dental procedure might be relevant.
“I don’t want to cause any alarm. No-one should consider cancelling or delaying any kind of surgery. But I think it would be prudent to do some research in this area going forward.
“No way is this suggesting Alzheimer’s is a contagious disease. You can’t catch it by living with someone who has Alzheimer’s or being a carer.”
Alzheimer’s is the most common form of dementia, whose distinguishing feature is memory loss and problems with thinking, language and problem-solving. It is progressive, meaning it worsens over time.
Disturbing figures show the UK is already in the grip of a dementia epidemic with a new case diagnosed every three minutes. By 2050 more than 2million will be struck down with the illness. It has been 12 years since the last treatment for dementia was licensed in the UK.
Dr Eric Karran, of Alzheimer’s Research UK, said: “Previous research has suggested the amyloid protein may behave in a similar way to the prion protein responsible for Creutzfeldt-Jakob Disease (CJD), but this study provides evidence amyloid could also be passed between humans through contaminated brain tissue.”
Richard Kerr, president of the Society of British Neurological Surgeons, said: “This is new information in a field of highly complex scientific enquiry that needs to be taken seriously.
“Further research is needed so we can learn more about transfer and whether existing decontamination procedures are effective. This will inform any clinical decisions that need to be taken to manage and reduce even the smallest risk to patients.”
Professor Damien Walmsley, scientific advisor to the British Dental Association, said: “Dentists take patient safety very seriously and follow strict protocols to protect patients from the risk of infections, however slight that risk may be.
“These protocols were strengthened in 2007 when a UK-wide restriction on the re-use of files that come into contact with nervous tissue during root canal treatments was put in place. These measures make dentistry one of the safest areas of healthcare.”
The research is published in the medical journal Nature.