Could your dog have dementia?

Chester was the pup of his pack back in the day.

"He was a spunky little thing," said owner Lucie Greco, a Malvern dog groomer. "Always on the go. Just a happy soul."

But last month, the little Pekingese turned 14 – up there in dog years. Lately, Chester has been having house-training "accidents," Greco acknowledged delicately. He never used to. At times now, he seems a touch confused, like the other morning when Greco woke him a bit too quickly. Chester nipped her.

"That's why I think he's getting a little, you know, dementia," Greco said. "He's going a little off."

Bark, bark, against the dying of light. Dogs and cats, like their human companions, can suffer the ravages of cognitive decline, also known as senility or dementia. There's a body of research that says it also appears to happen in the wild to some species of mammals and birds, even insects. However, animal experts add, creatures living in unprotected environments probably don't survive very long with serious cognitive loss.

Domestic animals, especially those that share our homes, are another story. Advances in veterinary medicine have made it possible for pets to live longer, just as medical breakthroughs have extended people's lives. Much of the research has focused on dogs; their decline has its own name – canine cognitive dysfunction (CCD).

"Certainly as we see dogs get older and older, we do see a higher proportion of them with signs" of CCD, said Evelyn Galban, associate professor of neurology and neurosurgery with the University of Pennsylvania veterinary school.

In some dogs, cognitive dysfunction can start to manifest as early as 8 years of age. It's not as common in cats, but when it does occur, it tends to happen at age 15 or over, Galban said.

The physiology of the decline, while still very much in the research stages, may cross species, too. Studies on the brains of dogs with CCD that have died have shown protein plaque build ups, not unlike those of humans, said Galban.

Before deciding that your four-legged friend has dementia, experts stress ruling out other health problems. A pet that has started soiling indoors, for example, may have a treatable bladder infection or kidney problems, not dementia.

There are other signs of cognitive dysfunction. A big one is a notable increase in anxiety. Senior dogs may seem alarmed by people or animals they know and even have always liked, including family members. Their sleep patterns can change greatly; they may start pacing through the night or engaging in nocturnal meowing or barking for no apparent reason. (That can also be a sign of thyroid problems – something else to rule out.)

Like people, animals with dementia can have times of total lucidity, but also periods of being confused and disoriented. Henry, my family's dearly departed beagle-basset mix, started slipping away for unauthorized walks late in life.