News release

From: Frontiers

Shorter strides can be an early warning sign of dementia in senior dogs, just as in people

Cognitive decline in dogs is associated with changes in the front legs’ gait, yielding a new monitoring tool for vets

Scientists have shown that the stride length of the front legs (but not the hind legs) of senior and geriatric dogs decreases as their cognitive performance worsens. In contrast, chronological age itself was a poor predictor of stride length. A similar reduction in step length has been well documented in people with dementia. These results suggest that a decline in stride length could be an early warning sign of canine dementia, and so an informative new tool for veterinarians.

Main text: The onset of dementia 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. These 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 have found a similar change in dogs with cognitive dysfunction syndrome, also known as canine dementia. Noting such a change in their pet could thus prompt owners to seek veterinary help earlier. The results are published in Frontiers in Veterinary Science.

“Here we show that 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,” said lead author Dr Natasha J Olby, a professor of veterinary neurology and neurosurgery at North Carolina State University.

Olby and colleagues followed 88 senior and geriatric dogs (females and males, and purebred or mixed breed) as part of the Longitudinal Study of Canine Neuroaging. These 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.

Longitudinal study of ‘neuroaging’

Dogs visited the laboratory for three days every six months for the remainder of their life. Here, they underwent a comprehensive battery 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, for example the Canine Dementia Scale (CADES) to measure cognitive impairment and the Canine Brief Pain Inventory (CBPI) to assess chronic pain.

A filmed assessment of gait speed and stride length formed an integral part of these visits. Dogs were set up to walk at their own pace along a five-meter-long walkway, while being held on a slack leash by the researchers. No verbal encouragement, treats, or other external motivations were given to them during these 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 analyses showed that this 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 CADES scores, indicating that as dogs age, greater cognitive decline results in shorter strides of the front legs.

On average, a 10-point increase in CADES translated into a 1.2% reduction in the relative stride length of the front legs. In contrast, 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.

Stepping down

“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,” said Olby.

“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.”

As expected, the relative stride length of the front legs also decreased with higher CBPI ratings, meaning that chronic pain further worsens the gait.

The authors 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 like orthopedic and spinal health can influence stride length, it could nevertheless be useful for clinical monitoring.

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