Dogs and cats in their dotage

Science News, Oct 17, 1998 by Susan Milius

Zappa made a big impression on Bill Ruehl when he was a student. That's not the rock icon of the 1960s but one of his lesser-known contemporaries, a much-loved, mixed-breed dog belonging to Ruehl's roommate.

Zappa (the dog) did not age gracefully. Despite having for years competently differentiated outdoors from in, Zappa lost his house-training. He also stopped sleeping normally and paced during the night. He got stuck in familiar rooms as if he couldn't work out the route past a chair or sofa. At least once a day, Ruehl or his roommate had to rescue the dog because he'd wandered to a neighbor's and been unable to find his way home.

Today, veterinarian William W. Ruehl is vice president of scientific affairs for Deprenyl Animal Health in Overland Park, Kan. The company has applied to the Food and Drug Administration to market what would be the first drug in the United States approved to treat behavior troubles of older dogs like Zappa.

Just the possibility that something could perk up doddering pets is stirring discussion of the mental problems of aged animals. The drug application has called attention to years of research exploring whether canine troubles resemble Alzheimer's disease in humans and whether drugs that affect human brain chemistry can help old animals.

Pets, like people, live longer now, thanks to advances in medicine and nutrition. The American Veterinary Medical Association estimates that the United States alone has more than 7.3 million dogs aged 11 or older, representing some 14 percent of the canine pets in the country. As the number of four-legged senior citizens grows, Ruehl and other veterinarians predict more age-related brain problems in pets, much like the rise in Alzheimer's disease in people.

Today, Zappa's diagnosis would be "cognitive dysfunction," but veterinarian Katherine A. Houpt remembers when such complaints were described as "fear of dying" in old pets. As director of Cornell University's Animal Behavior Clinic, she has seen a number of dogs whose behavior changed sadly in old age. Like Zappa, they soiled floors, paced at night, and got lost in their yards. Many eventually failed to recognize their owners.

These animals' personalities changed, too. One malamute-size dog refused to eat from a bowl anymore and hid under furniture. Formerly stouthearted sorts developed terrible thunder phobias. Another patient slept all day in the shower stall and spent the night digging around in closets and tearing at the furniture, acting like a dog left alone even though the whole family occupied their usual beds.

"It's really heartbreaking," Houpt says.

Like Alzheimer's disease in people, the diagnosis for cognitive dysfunction in dogs and cats comes after excluding other medical causes. Ruehl describes a hypothetical schnauzer who seems frequently disoriented and has started to circle in one spot for no apparent reason. Is its brain giving way?

It's a tempting diagnosis, Ruehl admits, but suppose the alert owner realizes the dog seems worst after meals. The schnauzer could easily have not a cognitive problem but a liver disorder that allows buildup of toxic by-products that cloud its brain.

David S. Bruyette of VCA/West Los Angeles Veterinary Medical Group has run across the opposite problem, people blaming what are cognitive problems in their pets on physical maladies. When owners tell him that old dogs are going deaf because they fail to respond to commands, Bruyette suggests an easy hearing test: Turn on the electric can opener. That's one of the last sounds a pet's dysfunctional brain fails to process, he says.

To estimate how many dogs develop cognitive dysfunction, Ruehl and Benjamin L. Hart of the University of California, Davis surveyed owners of nearly 140 dogs between the ages of 11 and 16 that had no known ailments. Sixty-two percent of the dogs showed at least one sign of cognitive decline, the researchers reported in Psychopharmacology of Animal Behavior Disorders (1998, Nicholas H. Dodman and Louis Shuster, eds., Blackwell Science). The survey probed four categories of complaints: failures in housetraining, changes in sleep patterns, disorientation, and changes in sociability.

Such a breakdown in brainpower can be just as life-threatening as failures in other organs, Bruyette points out. He made a presentation on cognitive dysfunction to the American Animal Hospital Association at this year's annual meeting in Chicago, and he has conducted clinical trials for Deprenyl Animal Health.

"Most commonly in veterinary medicine, [cognitive dysfunction] becomes a fatal disorder because the bond between the client and the pet has been broken," he says. "It's not the same pet anymore. The owner just gets frustrated." And the pet gets euthanized.

Are these symptoms inevitable on the last lap of normal aging in dogs, or does cognitive dysfunction mean the dog has an injured or diseased brain? "Nobody has the data to answer that question," says Gary M. Landsberg of Doncaster Animal Clinic in Thornhill, Ontario. Senility does not strike all dogs, he points out. "We have graceful agers--whether people or animals."