This fact check has been performed based on the information available on the date of publication. Read more about how we work here.
According to an article circulating on the internet, an infection in the nose could trigger Alzheimer’s disease. Nonsense, say experts. There is no evidence to support the hypothesis that Alzheimer’s is an infectious disease. Moreover, the study on which the article is based is of dubious scientific quality.
The post below (archived here) appeared on the Facebook page ‘Science in the Picture’, which has more than 58,000 followers.
The researchers have found a scapegoat’, reads the caption accompanying the link to an article that appeared on 24 February 2022 on the Dutch website Wetenschap in Beeld entitled ‘Researchers: Nasal bacteria can cause Alzheimer’s’.
Alzheimer’s is the most common form of dementia, a collective term for diseases that affect the brain. According to the World Health Organization (WHO), more than 55 million people worldwide suffer from Alzheimer’s.
“A very common nasal bacteria can affect your brain within a few days and increase the risk of Alzheimer’s,” the article reports. It bases that claim on the conclusions of a recent study from Griffith University in Australia. That study would show that bacteria from the nose can penetrate into the brain and start a chain reaction that leads to Alzheimer’s disease.
The study looked at a Chlamydia bacteria that causes various respiratory infections and could travel from the mucous membranes in the nose to behind the brain’s protective barrier in just 72 hours, at least in the mice in the study. In this way, the amyloid protein from the bacteria accumulates in the brain cells, and it is precisely this accumulation that is typical of Alzheimer’s disease.
Nonsense
De alzheimerexperten die Knack spoke are not impressed by the article or the study on which it is based. Molecular biologist and Alzheimer’s researcher Bart De Strooper (VIB-KU Leuven Center for Brain Research), who heads the Dementia Research Institute in London, puts it as follows: ‘This is absolute nonsense. I wouldn’t know what more to say about that. You may quote me like this.’
Professor of neurology Jan Versijpt (UZ Brussel), who specializes in cognitive disorders such as dementia, also strongly puts the conclusions of the above study into perspective. ‘What is posited in the article is part of the hypothesis that Alzheimer’s disease is an infectious disease. However, this is not a common hypothesis among scientists. For example, if you search the literature for a link between Alzheimer’s and the Chlamydia bacteria, you will find barely a hundred reports on it, which is particularly meager in that context and perfectly illustrates how little the hypothesis is alive, even though a lot of time and research has already been done. spent on.’
‘The infection hypothesis is also not consistent with the epidemiology’, continues Versijpt. The single greatest risk factor for Alzheimer’s is age. Those older than 90, for example, have a 1 in 3 chance of getting the disease.’
Versijpt also questions the cited research. ‘The amyloid protein produced in a Chlamydia infection is indeed one of the main proteins that accumulate in Alzheimer’s disease. But there is debate about whether that is the cause of Alzheimer’s disease. It can also be a side effect, while something else is triggering the disease. We also don’t yet know why the accumulation of that protein would lead to Alzheimer’s in some people and not in others. Much more scientific research is needed for a conclusive answer to that question.’
Aging brain
Moreover, Versijpt emphasises, research in mice cannot simply be extrapolated to humans. ‘In the study in question, the mice were not tested cognitively either, the conclusion is based solely on the presence of that specific protein. You also always have to take into account that an aged brain works differently from a young brain, and in mouse experiments, young animals are usually used.’
Molecular cell biologist Wim Annaert, who studies Alzheimer’s disease at the Center for Brain Research (VIB-KU Leuven), also does not endorse the conclusions of the research in question. ‘This is clearly over-interpretation in a scientifically weakly substantiated study’, he says on the phone. ‘For the study, healthy mice were infected with the Chlamydia bacterium, after which the extent to which the amyloid protein in the bacterium accumulated was examined. But in healthy mice it is difficult to detect that specific protein. There is a risk that you also include other proteins. Moreover, you should also include mice in the study that are less healthy, in order to see whether their condition worsens. The study therefore has little scientific value.’
‘If you could get Alzheimer’s from such an infection through the nose, then in the statistics we would also see more cases in young people, which is not the case: Alzheimer’s is typically a disease that occurs later in life. If the disease were the result of an inflammation that affects the brain in a few days, then the disease would also be very acute. That is not the case,’ says Annaert.
Conclusion
According to a widely read article circulating the internet, research has shown that an infection in the nose could lead to Alzheimer’s. Experts say that is unlikely. There is virtually no evidence to support the hypothesis that Alzheimer’s is an infectious disease. Moreover, the study on which the article is based has quite a few flaws. We therefore rate the claim as untrue.
Sources
In the article you will find links to all sources used.
In addition, the following people were contacted for this fact check:
– Mail traffic with Bart De Strooper on November 14, 2022
-Telephone interview with Jan Versijpt on November 14, 2022
– Telephone interview with Wim Annaert on November 16, 2022
All sources were last consulted on November 17, 2022.