Cats that exhibit dementia-like symptoms in their senior years undergo changes analogous to those seen in humans with Alzheimer’s disease, as highlighted in a study I found. This finding may open pathways for new research and help in discovering treatments for these challenging and notorious diseases.

“Our advancements in treating Alzheimer’s disease have been relatively limited compared to other illnesses,” stated Dr. Robert McGeechan, the study’s lead author, in an interview with BBC Science Focus.

“Cats are experiencing similar neurological changes, making them potentially more relevant models for understanding the disease. By investigating Alzheimer’s in cats, we can develop treatments that might be more effective for humans.”

Alzheimer’s disease is the most prevalent form of dementia, encompassing a range of neurodegenerative conditions that impair memory, problem-solving, language, and behavior. Approximately one in nine individuals over 65 are affected by Alzheimer’s, and with an aging global population, over 150 million people could be diagnosed by 2050.

Yet, despite decades of investigation and billions spent, only a handful of effective treatments exist today.

How Cats Develop Dementia

The understanding that cats can show dementia-like symptoms with age is not new. According to some research, nearly one-third of cats aged 11 to 14 exhibit at least one sign of cognitive dysfunction syndrome (CDS), the veterinary term for dementia in felines. For cats older than 15, this figure increases to over half.

CD symptoms in cats, which resemble those in humans with Alzheimer’s, include changes in sleep patterns and disorientation. Many cats also become more vocal and often seek additional comfort and attention from their owners.

It is also known that, similar to humans, older cats typically develop an accumulation of amyloid beta plaques in their brains, which are suspected to play a role in the onset of Alzheimer’s.

“As we age, humans develop these protein plaques in our brains. However, not everyone with these plaques develops Alzheimer’s, and the reasons for this remain unclear,” McGeechan explained.

“We were similarly situated with cats, knowing they could develop dementia and that some produce these proteins as they grow older, but we lacked clarity on whether this was solely age-related or if it contributed to dementia.”

To delve deeper, McGeechan’s team examined the brains of 25 cats of varying ages post-mortem, including those with CDS symptoms.

They discovered that amyloid beta plaques were not just passively situated in the brain but were also linked to detrimental changes. Notably, they observed increased inflammation and signs of glial cells, the immune cells of the brain, “enveloping” the synapses surrounding these protein plaques.

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Synapses are tiny junctions enabling brain cells to communicate, and their progressive loss is believed to underlie many memory and behavioral symptoms associated with dementia.

The findings imply that a similar toxic chain reaction may also occur in feline brains. As amyloid beta accumulates, it activates glial cells, leading to the degradation of healthy synapses. While this broader pattern was evident, the finer details proved to be more intricate.

Upon comparing the brains across different age groups, subtle differences emerged. Cats with dementia appeared significantly different from younger cats, exhibiting greater amyloid plaque accumulation, inflammation, and synaptic loss. However, they did not starkly differ from older, yet otherwise healthy cats.

This observation indicates that researchers might struggle to draw a clear line between aging and dementia.

Yet, the team noted an important distinction concerning the relationship between amyloid plaques and synaptic damage. In older, healthy cats, increased amyloid did not equate to more harm. However, in cats with dementia, higher plaque levels correlated with increased inflammation and greater brain cell loss.

McGeechan posits that this mirrors human scenarios. Numerous older adults accumulate amyloid plaques in their brains without developing Alzheimer’s, while others experience significant cognitive decline.

“Amyloid may have a more toxic impact on cats experiencing CDS,” he noted. “This correlation suggests amyloid plays a role in inflammation and synaptic loss in the dementia group, unlike in the aging group.”

Thus, while amyloid accumulation may contribute to feline dementia, it likely does not tell the full story. Much like Alzheimer’s in humans, a complex interplay of various factors may also be at play.

The Significance of Cats in Research

Alzheimer’s disease research has historically depended on rodents, where diseases are artificially induced by genetic manipulation.

While these models aid in exploring molecular mechanisms, they often fall short of encapsulating the intricacies of naturally occurring diseases that unfold over time. Consequently, numerous promising drugs that succeed in mice fail when tested on humans.

In contrast, cats naturally develop dementia as they age, mirroring the human experience. They also share the same living environments and risk factors, including diet and air quality.

This similarity renders them a more realistic model for understanding disease biology and identifying environmental triggers that might push certain individuals towards dementia.

“Cats could serve as a bridge in our pursuit of effective treatments,” McGeechan expressed.

Future Directions

At this point, the findings raise just as many inquiries as they resolve. Given that the study involved only 25 cats, a larger sample size may be necessary to clarify the precise mechanisms underlying the observed clinical outcomes, according to McGeechan.

Another area of focus is tau. Besides amyloid beta, tau is another key protein associated with Alzheimer’s disease. Unlike amyloid plaques, tau forms tangles within brain cells. Many researchers believe tau drives the most severe stages of the disease in humans, but this investigation did not address tau in cats.

Dogs may also present a valuable avenue for exploration. Like cats, they can age into a dementia-like syndrome, displaying symptoms recognizable to many owners, such as sleep disturbances, anxiety, and forgetfulness. Comparing the brains of dogs and cats might reveal shared biological processes across species.

Ultimately, this body of research holds promise not just for human health.

“Dementia in cats is a distressing condition for both the animals and their owners,” remarked Professor Danièlle Gunn-Moore, a co-author of the study and a chair in feline medicine at the Royal (Dick) School of Veterinary Medicine.

“Conducting such research aims to enhance our understanding of how best to treat these conditions. This work benefits not just cats and their owners but also individuals with Alzheimer’s disease and their loved ones. Dementia in cats serves as an ideal natural model to study Alzheimer’s disease.”

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About Our Experts

Robert McGeechan is a resident in Veterinary Neurology and Neurosurgery and serves as an ECAT Veterinary Clinical Lecturer at the University of Edinburgh, UK. His research has been published in European Journal of Neuroscience, Scientific Reports, and Nature Neuroscience.