Around the time Dante turned 8, he started to seem a little off. The 70-pound Bernese mountain dog would pace his family's home like a caged bear. Then he would stand stock still, staring trance-like at a corner of a room. In the middle of the night, he would begin barking incessantly. Then the indoor incontinence began.
A brain scan confirmed that Dante had canine cognitive dysfunction, colloquially known as doggy dementia. It is often described as the dog's analog to Alzheimer's disease. Some studies have found it can occur in 14 to 35% of older dogs. But because the symptoms resemble those of other diseases, it's difficult to confirm.
A large new study of 15,019 dogs enrolled in the Dog Aging Project, an ongoing investigation into canine illness and aging, identifies the top factors associated with a dog's risk of getting the disease.
A key finding in the study, published in the journal Scientific Reports: Exercise may play a significant preventive role. The odds of a cognitive dysfunction diagnosis were 6.47 times higher in dogs reported as not active compared with those reported to be very active, researchers at the University of Washington found. But because the disease itself could lead to lack of exercise, the study results, which are based on observations by owners, suggest correlation, not causation.
Odds of getting the disease also appear to increase in dogs that have neurological disorders, or impaired hearing or sight.
"When you don't get stimulation from the outside world, it seems to increase the risk of our not even being able to use our brains as well," said Annette Fitzpatrick, a co-author of the study and a University of Washington research professor,
And age matters. A dog's life expectancy often depends on breed, size and body mass: think mastiff (six to 12 years) vs. Chihuahua (12 to 20 years). During the later years of a dog's projected life span, each successive year contributed to the potential for disease onset, the study found.
In fact, the researchers noted, risk factors that correlate with canine cognitive dysfunction mirror some of the factors for humans with dementia, including Alzheimer's disease.
Earlier studies of canine cognitive dysfunction often drew from veterinary assessments in smaller populations of older dogs; this one is culled from dogs that range in age from puppyhood to mid-20s. In the coming years, as these dogs grow older, the project, which has enrolled more than 40,000 dogs and hopes to reach 100,000, will issue more complex findings on cognitive dysfunction and other diseases.
The results were derived from just one baseline accounting by owners of their dog's health and lifestyle experience between 2019 and 2020, and a particularly high-threshold cognitive function questionnaire. Among the questions: How often does your dog pace up and down, walk in circles and/or wander with no direction or purpose? How often does your dog get stuck behind objects and is unable to get around? How often does your dog walk into walls or doors? How often does your dog have difficulty finding food dropped on the floor?
If the study findings have a familiar, even intuitive ring, that may be because the Dog Aging Project, which receives funding from the National Institute on Aging, a branch of the federal National Institutes of Health, may shed insight into factors that affect the life span of humans as well as the dogs who share their homes.
Unlike laboratory animal subjects such as fruit flies and mice, companion dogs are affected by their owners' environmental and social factors, such as secondhand cigarette smoke, lawn pesticides and access to health care.
"Estimates of human longevity say that about 75% is due to environment and 25% is genetic," said Matt Kaeberlein, a biogerontologist at the University of Washington who is a co-director of the Dog Aging Project. "So companion dogs give us the opportunity to really understand the role of that environmental variability in the biological aging process."
Moreover, because dogs age much more rapidly than humans, the studies underway within the project provide opportunities along an expedited timeline for insights into human and canine aging.
Although there are medicines and diets that can ameliorate the dog's cognitive dysfunction for a time, Dr. Nicole Ehrhart, a veterinarian and director of the Columbine Health Systems Center for Healthy Aging at Colorado State University, said owners needed to be sensitive to their dog's increasing disorientation. Don't disrupt their routines. Don't move around furniture. Secure your yard, so the dog can't wander away and get lost. And know that dogs, like older humans, can get "sundowner syndrome": increased anxiety and disorientation as the day comes to a close.
"It turns out that probably the best model for human aging has been aging alongside of us for hundreds and hundreds of years," Ehrhart said. "This is a two-way street: Anything we're going to be doing to improve our dogs' health and life span is likely to improve ours, and anything we're doing for humans is very likely to improve our dogs. And who doesn't want that?"