Circumstantial evidence for the transmission of Alzheimer’s from one person to another through surgery, medical procedures is growing.
Once again, scientists have raised the specter of Alzheimer’s as an infectious disease, theorizing it could be transmitted through some medical procedures and surgeries. Though this possibility is purely theoretical, the “circumstantial evidence for such transmission” is growing, say Swiss and Austrian researchers.
Their new study focuses on patients with Creutzfeldt-Jakob disease, who, many years before their deaths, had received surgical grafts of dura mater, the membrane that covers the brain and spinal cord. During autopsies, researchers discovered amyloid-β protein, the hallmark of Alzheimer’s disease, in the grey matter and blood vessels of their brains. Such results seemed unusual in patients so young — they were between the ages of 28 and 63 — especially since none had a family history of early-onset dementia.
For comparison purposes, then, the scientists performed another round of autopsies on 21 control patients who died of Creutzfeldt-Jakob disease at similar ages but had not received surgical grafts. However, none of these 21 comparison cases had the pathological signs associated with Alzheimer’s disease.
Based on this outcome, the researchers say it is “plausible” that the Alzheimer’s pathology may have resulted when small seeds of amyloid-β protein, a hypothesized trigger for dementia, were transferred from the grafts and transplanted in the patients' tissues. The grafts having been prepared from human cadavers provides added weight to this theory.
“Yet, alternative explanations are also possible,” wrote the team in their published paper. Despite this caveat, their research echoes a previous study published this past September.
Sterilized Surgical Instruments May Be Contaminated
In September 2015, University College London scientists theorized that the signature Alzheimer’s proteins had spread via a hormone treatment prepared from cadavers based on their own autopsy results. Here, the British researchers conducted autopsies, including extensive brain tissue sampling, on eight patients with Creutzfeldt-Jakob disease.
While all the brains revealed the signature signs of Creutzfeldt-Jakob, six exhibited the amyloid-β pathology associated with Alzheimer’s as well. At death, these patients had been between the ages of 36 and 51. Once again, these patients were unusually young to display even the earliest signs of Alzheimer’s, yet none had a genetic history of early-onset Alzheimer’s.
One thing they did have, though, was a shared history of treatments with human growth hormone extracted from cadaver-sourced pituitary glands. The hormone treatments began in 1958 and ceased by 1985 following reports of Creutzfeldt-Jakob disease occurring among recipients — some of the treatments had been contaminated with prions, the infectious agent linked to that disease.
Analyzing the data, the British scientists hypothesized Alzheimer’s may be transmissible in a manner similar to Creutzfeldt-Jakob disease. Potentially, the proteins found in the brains of Alzheimer’s patients could be spread to others by way of contaminated surgical instruments because the proteins are able to survive sterilization with formaldehyde.
Blood transfusions may also be a route of transmission, the scientists said, as is the case with Creutzfeldt-Jakob disease.
However, the scientists warn their findings are hypothetical. Strictly speaking, if transmission did occur, that only happened by way of the cadaver-derived human growth hormone injections, no longer in use. Cadaver-derived hormones and membranes have since been replaced with synthetic growth hormones and synthetic membranes.
Earlier, 2015, a potentially explosive study has provided the first evidence that the devastating condition can, like mad cow disease, spread through 'medical accidents'. The British researcher, Professor John Collinge, said we 'need to rethink our view of Alzheimer's and evaluate the risk of it being transmitted inadvertently to patients'. Following the second case, he told Nature 'Our results are all consistent.
'The fact that the new study shows the same pathology emerging after a completely different procedure increases our concern.'
Neither study implies that Alzheimer's disease could ever be transmitted through normal contact with caretakers or family members, the scientists emphasize.
One of the UK's leading brain surgeons warned that we don't know if the techniques used sterilize medical instruments are effective and said that the research 'must be taken seriously'. However, others urged caution, saying the study was small and it does not prove that Alzheimer's disease is contagious.
Professor Collinge, of University College London stumbled on the link with Alzheimer's when inspecting the brains of eight people who had died from CJD, the human form of mad cow disease. They had caught CJD after being given injections of human hormones as children to treat growth problems. To his great surprise, he found a protein that is a hallmark of Alzheimer's in the brains of seven of the eight of the patients. In four of them, levels of the memory-robbing amyloid beta protein were 'severe'.
Writing in the prestigious journal Nature, he said that those studied were aged between 36 and 51 and such brain damage is 'simply not seen' in people of that age. With no evidence that CJD somehow triggers the build-up of the protein, Professor Collinge said the most likely answer is that it, like the CJD, had been lurking in the hormone injections. None had actually developed full-blown Alzheimer's but they may have done if they had lived longer.
What does it mean for me?
It raises concerns that the Alzheimer's amyloid beta protein can be passed between people in the same way as CJD. This means that it could potentially be spread via blood transfusions, brain surgery and corneal transplants.
Even dentistry may be a risk. Lead researcher Professor John Collinge stresses that his study provides no evidence that dental work is dangerous. However, he also said such possibility may need to be considered.
But aren't medical instruments sterilized?
Yes but the amyloid beta protein clings to metal and is resistant to boiling water and formaldehyde.
Some experts say more research is needed but the Department of Health says there is no cause for concern and that the NHS has 'extremely stringent' procedures to minimize infection risk from surgical equipment.
Many dental instruments are only used once and the study doesn't mean Alzheimer's can be caught by everyday contact such as kissing or by caring for someone with the disease.
Addressing the recent findings, the Government Chief Medical Officer, Dame Sally Davies, said: “There is no evidence that Alzheimer’s disease can be transmitted in humans, nor is there any evidence that Alzheimer’s disease can be transmitted through any medical procedure”.
Sources and Additional Information: