The new findings published in Nature will no doubt reignite debate over whether the disease is caused by an infectious microbe.
The new research suggests that Alzheimer’s disease is caused by a fungus growing in the brain. Yeasts and molds were found in grey matter and blood vessels of all the dementia patients studied. In stark contrast, the brains of healthy people were free of fungi.
The Spanish researchers said fungal infection could “readily explain” all the symptoms of Alzheimer’s – and may be the cause of the neurodegenerative disease. The study, published by the highly respected Nature group of journals, is the second in a matter of weeks to question whether it is possible to catch the devastating condition.
Last month, UK research suggested it could be spread through blood transfusions, operations and even dental work. Before that, it was thought that Alzheimer’s was either caused by faulty genes or a combination of bad luck and aging.
The latest study will further fuel fears that Alzheimer’s can be caught. However, it could also lead to much-needed new treatments for a disease that affects nearly 44 million people worldwide and robs people of their speech, memory and dignity. However, much more work is needed to confirm the link.
Researchers from the Autonomous University of Madrid found traces of several different types of fungus in the brains of 11 people who had died with Alzheimer’s disease. They said the range of fungi might help explain why the disease can vary so much from patient to patient. And that symptoms of Alzheimer’s disease, including its slow progression and the involvement of the immune system, can be “readily explained” by a fungal infection.
Writing in the journal Scientific Reports, they added that if the condition is caused by a fungus, this could help explain why drug trials until now have had disappointing results. It also means that existing antifungal drugs may be powerful weapons in the fight against Alzheimer’s. Lead researcher Luis Carrasco said, “It is evident that clinical trials will be necessary to establish a causal effect of fungal infection in AD. There are a number of highly effective antifungal compounds with little toxicity. A combined effort from the pharmaceutical industry and clinicians is needed to design clinical trials to test the possibility that Alzheimer’s disease is caused by fungal infection.” However, he also cautioned that his study does not prove that Alzheimer’s is triggered by a fungus. It is also possible that the fungal infection may follow Alzheimer’s disease, with yeasts and molds finding it easy to take hold in brains already weakened by dementia.
Sylvain Lehmann, a French researcher on neurodegenerative disease, described the results as “very speculative” and British experts urged caution. Dr. Laura Phipps, of charity Alzheimer’s Research UK, said, “While this very small study suggests that fungal cells may be present in the brains of people with Alzheimer’s, we cannot conclude from this work that such infections cause or increase the risk of the disease. Without a corresponding medical history, we do not know whether the fungal infection occurred before or after the onset of Alzheimer’s disease, or whether this group of people had an increased risk of fungal infection due to other health complications. The best current evidence suggests that eating a healthy and balanced diet, not smoking, staying physically active and keeping weight and blood pressure in check can all help reduce the risk of dementia.”
However, she added that the charity is funding research into whether infections play a role in Alzheimer’s. Dr. Clare Walton, of the Alzheimer’s Society, said, “Traces of fungus in the brains of these few people with Alzheimer’s is not enough to conclude that it plays a role in the development of the disease. Although there has been research in the past to explore whether infectious diseases can raise the risk of developing Alzheimer’s disease, the results have so far been inconclusive. We do know that Alzheimer’s disease weakens the internal barrier that protects the brain and this may make it more open to infections. There is still much research to be done in order to truly understand the causes of dementia. As it is a progressive, long-term condition, it can take many years before symptoms appear and so it is hard to determine the initial cause based on samples taken after death.”