Is Alzheimer's disease contagious? The science still says no

Is Alzheimer's disease contagious?

Alzheimer’s disease is not contagious, but caused by diseases of the brain from a complex mix of our genes and environment. 

Our research team at Alzheimer’s Society take a look at the evidence to bring you the real story. 

Why are papers asking if Alzheimer's is contagious?

The newspaper reports focus on new research which found a toxic form of the amyloid protein, a key hallmark of Alzheimer’s disease, could be transferred between people in very specific situations. 

The researchers at University College London looked at a rare type of surgery. This involved infusing growth hormone into people who aren’t able to produce enough. Today a synthetic hormone is used, but in the past it was taken from people who had died.

‘Most importantly, this procedure has been phased out for over 35 years.’

The study found that the infusion contained the toxic form of amyloid. A small number of people who had this surgery in the 1970s showed build-up of amyloid protein in their blood vessels. This resulted in damage to the surrounding brain tissue – a condition known as cerebral amyloid angiopathy. However they did not have Alzheimer’s disease.

The researchers also showed evidence that this transmissible form of amyloid could cause similar effects in the brains mice. Although not in all the models of mice tested. It’s also important to remember – what is true in mice might not be true in humans!

What does this research mean?

The researchers and other experts emphasise that this does not suggest that Alzheimer’s disease is contagious. Nor that the people studied or the mice developed Alzheimer’s disease. However the researchers do argue that the people affected may have gone on to develop Alzheimer’s with time.

We still don’t know enough about how amyloid protein might be transmitted between people to be certain about any risk. Current surgical methods are strict in their cleaning and disposal of all tools that could become contaminated. 

Further research is needed to be sure whether this is enough. All surgical interventions come with risks; at present the risk of transmission of Alzheimer’s disease seems to be a very low.

Our Head of Research at Alzheimer’s Society, Dr James Pickett, clarified the study findings. 

'We’ve known for a long time that amyloid protein is involved in Alzheimer’s disease, but it is just one component. Although researchers found that some of the people who received this procedure had changes in their brain related to the amyloid protein, they didn’t have Alzheimer’s disease itself. The procedure in this study was phased out over 35 years ago, and more modern approaches do not have the same risk of exposure. 

'There remains absolutely no evidence that Alzheimer’s disease is contagious.

‘There are no examples of Alzheimer’s being transmitted from person to person via any current surgical procedures.’

‘There is also good evidence to show that blood transfusions don’t increase your chances of developing Alzheimer’s disease.'

Should I delay medical treatment because of the research?

The researchers in the study, and other experts in surgery and dementia, were quick to reassure that any risk of amyloid being transferred between people is very small.

Professor Bart de Strooper, Director of the Alzheimer’s Society co-founded UK Dementia Research Institute said:

'There is absolutely no reason to postpone or decline brain surgery based on the current evidence'

He also noted that large population studies of almost 1.5 million people in Sweden and Denmark found no evidence that blood transfusions could increase the risk of developing dementia.

What will happen now?

Researchers will continue to investigate if there is any risk that amyloid proteins could be transferred between people. Even if the risk is small, it is important to check we are doing all we can to avoid harm. We would expect this new research to tell us whether there are any other steps that we might need to take to be sure.

Dementia and Alzheimer’s disease are not contagious. They are caused by diseases of the brain, but we can’t catch them from other people. We do know though that there are things we can all do to reduce our risk of developing dementia, like eating a healthy balanced diet, staying active and stopping smoking.

If you are worried about your memory or changes to your thinking skills contact your GP.