Do Cats Get Dementia?

Babycat may have been a “naturally occurring model of Alzheimer’s disease,” according to a new report in The European Journal of Neuroscience, from researchers at the Universities of Edinburgh and California, the UK Dementia Research Institute, and Scottish Brain Sciences.

What I’ve long thought of as a curiosity amongst one of our 16 felines might actually have been dementia.

When Babycat began frantically and plaintively meowing at the corner of the ceiling in the bedroom closest to my head, we thought he was answering the scratches of rodents in the attic above, and searched. But mouse turds in an attic are a constant – what was provoking Babycat’s distress? Our other six felines were undisturbed.

In retrospect, and after reading the neuroscience article, I think that Babycat had “feline cognitive dysfunction syndrome,” aka feline dementia, an “age-related neurodegenerative disorder.”

Cat parents and vets often don’t recognize the condition, perhaps because of the overlaps with normal cat behavior. Cats can do strange things for awhile, and then stop doing them. But Babycat’s behavior only worsened.

Behavioral Changes

The article helpfully lists the behavioral changes seen among ““elderly cats”:

• increased vocalization, especially at night
• altered social interactions, but that was hard to detect in a house with six felines
• seeking attention
• disrupted sleep–wake cycle. Cats sleep nearly all the time, so that’s easy to spot.
• ignoring the litter box, a symptom termed “house-soiling.” In a multi-cat household, that’s common.
• altered activity level, disorientation, anxiety, and confusion
• learning or memory deficits. Babycat wasn’t obviously attempting to learn anything, ever, and he didn’t seem to forget where he was. He was, in fact, more sensitive.

According to the report, imaging Babycat’s brain might have revealed atrophy, loss of neurons, microbleeds, and the telltale amyloid-beta plaques between neurons and black tangles of tau protein inside neurons, both proteins in excess and gumming up the works. We don’t yet know about loss of synapses – the critical spaces between neurons – and inflammation, critical parts of the disease process.

In mice and humans, microglia and astrocytes glom onto and engulf the all-important synapses, blocking transmission of nerve impulses. The process is normal during early development, and is called “synaptic pruning,” but is excessive in Alzheimer’s disease. This would presumably be true for cats too.

(Quick biology tutorial. The major cell type of the nervous system is the neuron, but cells call neuroglia are critical too. These include astrocytes, microglia, oligodendrocytes, microglia, and ependymal cells in the central nervous system and Schwann cells and satellite cells in the peripheral nervous system.)

Like Alzheimer’s disease in people, in felines it is age-related. Studies are scant, but in one, 28% of cats aged 11–14 years had at least one clinical sign of dementia, rising to 50% for cats over 15 years.

If feline dementia indeed serves as a model of Alzheimer’s disease, we may have something to learn from them about the pathogenesis and they may even serve as animal models to test treatments.

The new study used immunohistochemistry and confocal microscopy to examine brain slices from 7 young cats, 10 old ones, and 8 who seemed to have had dementia, after they had crossed the Rainbow Bridge naturally. Indeed, the brains of the older cats and those with dementia showed excess synaptic pruning. Nerve connections vital to memory were disappearing.

“These findings suggest that amyloid-beta exerts a pathogenic effect in the feline brain, with mechanisms mirroring those seen in human AD,” the investigators conclude.

If cats develop a feline version of Alzheimer’s disease, they would be invaluable animal models, because mice and rats do not get dementia. But being veterinarians, the researchers are also seeking to relieve dementia symptoms in pet cats.

Said Danièlle Gunn-Moore, Personal Chair of Feline Medicine at the Royal School of Veterinary Studies, “Feline dementia is so distressing for the cat and for its person. It is by undertaking studies like this that we will understand how best to treat them. This will be wonderful for the cats, their owners, people with Alzheimer’s and their loved ones. Feline dementia is the perfect natural model for Alzheimer’s, everyone benefits.”

Added lead researcher Robert McGeachan, also from the School of Veterinary Studies, “Dementia is a devastating disease – whether it affects humans, cats, or dogs. Our findings highlight the striking similarities between feline dementia and Alzheimer’s disease in people. This opens the door to exploring whether promising new treatments for human Alzheimer’s disease could also help our ageing pets. Because cats naturally develop these brain changes, they may also offer a more accurate model of the disease than traditional laboratory animals, ultimately benefiting both species and their caregivers.”