The endless meowing and stumble of an old, grumpy cat may indicate significantly more than feline aging: Japanese scientists have discovered protein deposits found in human Alzheimer's patients in the brains of wild cats.

Not only does the new study, published in the journal PloS ONE, provide new insight into the feline aging process, it may also offer clues into how the mind-robbing disease works. Scientists at the University of Tokyo examined the bodies of 14 Tsushima Leopard cats. The Tsushima Leopard cat is an endangered species that lives on the western Japanese island of Tsushima.

Investigators found that brain tissue from five of the cat carcasses contained Neurofibrillary tangles, or NFT, a protein commonly found in human Alzheimer's patients but rarely found in animals. Researchers also detected traces of the peptide AB42, also known to cause mental deterioration in the brains of cats in the study.

"If we closely compare changes in the brain among many different animals, we may be able to contribute to a study into the mechanism of the disease," said James Chambers, an assistant professor of veterinary pathology at the University of Tokyo, according to Kyodo News.

Chambers and his team said that there is no way to determine whether the Tsushima cats displayed dementia-like symptoms because the cats were not monitored when they alive. Researchers hope to conduct a similar study on house cats, which have been known to become irritable, forget their food, walk sideways and display other aging behaviors.

Researchers have long suspected that animals suffer from a similar kind of dementia seen in humans.

Recently, scientists at the University of California Davis found that nearly a third of dogs between the ages of 11 and 12 years old and 68 percent of dogs between the ages of 15 and 16 develop some sign of cognitive impairment. US researchers also found that 28 percent of cat between the ages of 11 and 14 years old also showed signs of dementia.

Veterinarians recommend that pet owners keep their pets healthy to prevent dementia because, like humans, a well-balanced diet, stimulation and companionship are key factors to reversing mental decline in animals.