Study suggests some dolphins may have Alzheimer’s disease

London (CNN) — According to a new study, the brains of three species of dolphins found stranded off the coast of Scotland show hallmarks of Alzheimer’s disease, providing insight into the disease in species other than humans.

According to the researchers, the findings could also provide a possible answer to the unexplained stranding of dolphins along the coast.

Alzheimer’s disease is a common neurodegenerative disease that mainly affects older people, with symptoms including memory loss, forgetfulness and confusion.

According to a study published Dec. 13 in the European Journal of Neuroscience, Scottish researchers conducted post-mortem studies on the brains of 22 toothed whales, making their findings more detailed than others, according to the authors.

All the specimens studied have washed up on the Scottish coast, like this white-beaked dolphin on Montrose beach. (Credit: Steve Black/Shutterstock)

“It is deeper and broader because it looks at a larger number of animals from several different species of cetaceans that are known to be of (older) age for the species,” said Mark Dagleish, co-author and Chief Medical Officer of Anatomical Pathology of the University of Glasgow.

The study analyzed specimens of five species: gray dolphin, pilot whale, white-beaked dolphin, harbor porpoise and bottlenose dolphin. Of the 22 studied, 18 were aged specimens.


Bottlenose dolphins were one of five species examined in the recent Alzheimer’s disease study. Credit: Adobe Stock

“Essentially, whole brains (were) examined to provide patterns of lesions (abnormalities) using more markers of Alzheimer’s disease,” Dagleish added, using the same techniques used for human tissue.

The results showed that three aging dolphins – a pilot whale, a white-beaked dolphin and a bottlenose dolphin – had brain changes, or lesions, associated with human Alzheimer’s disease.

Tara Spiers-Jones, another of the study’s co-authors, said this week that the researchers “were fascinated to see brain changes in aging dolphins similar to those in humans (aging) and the disease of ‘Alzheimer’s’.

“Whether these pathological changes contribute to the stranding of these animals is an interesting and important question for future work,” said Spiers-Jones, professor of neurodegeneration in the dean of biomedical sciences at the University of Edinburgh. .

alzheimer's dolphins

The pilot whales were among three aging dolphins with lesions similar to those of humans with Alzheimer’s disease. Credit: eco2draw/iStockphoto/Getty Images

The researchers found that the samples had accumulated phospho-tau proteins and glial cells and had formed plaques of beta-amyloid, the aggregate of a protein found in the brains of people with Alzheimer’s disease. The distribution of these lesions was comparable to that of brain regions in humans with Alzheimer’s disease, according to the research paper.

According to Dagleish, these results are “the closest we have found to demonstrating that an animal spontaneously develops the lesions associated with Alzheimer’s disease”, which was previously thought to occur only in humans.

Toothed whales often wash up in groups on British shores, which the study authors say could support the “sick leader” theory, in which the group follows an elderly leader into shallow waters, maybe due to confusion.

The similar neuropathology of aged dolphins and humans with Alzheimer’s suggests that marine mammals are susceptible to the disease, but Dagleish said a diagnosis can only be made if there are cognitive deficits. These are usually detected by cognitive impairment assessments, which is not possible with post-mortem studies.