Shorter strides may be early warning sign of dementia in dogs

By Stephen Beech

Shorter strides can be an early warning sign of dementia in dogs as well as people, according to new research.

Veterinary scientists have found that cognitive decline in man's best friends is associated with changes in the front legs’ gait.

They say the discovery provides a new way for dog owners to monitor the possible onset of dementia in their pets.

Previous research has shown that the onset of dementia in humans often comes with a change in gait. For example, years before they display any loss in memory, patients may start to walk more slowly with shorter, uneven and sometimes shuffling steps.

The changes are thought to be driven by a deterioration in the function of the brain’s frontal cortex and the cerebellum, which are responsible for planning and monitoring movement.

Now, scientists in the United States have found a similar change in dogs with cognitive dysfunction syndrome, also known as canine dementia.

Noting such a change in their pet could prompt owners to seek veterinary help earlier, according to the study published in the journal Frontiers in Veterinary Science.

Lead author Natasha Olby said: "The length of front leg stride taken by dogs decreases with age, but even more importantly, decreases with a cognitive impairment.

"In fact, we found that the effect of cognitive decline is larger than the effect of age by itself."

Olby, of North Carolina State University, and her colleagues followed 88 senior and geriatric dogs — females and males, and purebred or mixed breed — for the research.

The pets had been enrolled in the study upon reaching 75% of the life expectancy for their size and breed, corresponding to 12.7 years old on average.

Dogs visited the laboratory for three days every six months for the remainder of their lives.

They underwent a series of physical, neurological, physiological and orthopedic examinations, including tests for cognition, mobility, vision, hearing and strength.

Each time, owners were asked to fill out questionnaires about their companion’s health and behavior.

A filmed assessment of gait speed and stride length formed an integral part of the visits.

Dogs were set up to walk at their own pace along a 5-meter walkway, while being held on a slack leash by the researchers.

No verbal encouragement, treats or other external motivations were given to them during the trials.

Two key measures analyzed were the dogs’ absolute average stride length and their relative average stride length, adjusted for body size.

The relative stride length of the front legs tended to decrease across visits.

But more detailed analysis showed that the reduction was not driven to a significant extent by increasing age itself when age and cognition were included in the same statistical model.

Rather, the relative stride length decreased with worsening scores, indicating that as dogs age, greater cognitive decline results in shorter strides of the front legs.

But the relative stride length of the hind legs did not significantly change over time, either in association with greater chronological age or worsening cognitive performance.

Olby said: “It is fascinating to see that cognitive decline affects front legs and hind legs differently.

"In dogs, the hind legs are important for moving forwards, while the front legs also change direction and initiate braking.

“The cerebral cortex integrates more sensory information into the neuronal circuits which produce steps in the front legs, and so loss of high-level sensorimotor integration affects them differently.”

The research team concluded that front leg stride length is an objective measure of mobility that reflects changes associated with age-related cognitive decline — and, to a lesser degree, chronic pain — in dogs.

While other factors such as orthopedic and spinal health can influence stride length, they say it could nevertheless be useful for clinical monitoring.

Olby added: “If owners notice that their dog's front leg stride is becoming shorter they should visit their vet, for there are possible alternative causes such as arthritic pain or neck issues that can be treated.

“If a diagnosis of cognitive decline is made, there are likewise several lifestyle interventions that can be made, even if there is currently no cure.”