Anxiety and Impulsivity Are Associated with Premature Graying in Young Dogs

November 8, 2016
JoAnna Pendergrass, DVM

Dr. Pendergrass received her DVM degree from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory Universitys Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner ofJPen Communications, a medical communications company.

A recent study reported a significant association of anxiety and impulsivity with premature muzzle graying in young dogs.

Authors of a recently published study in Applied Animal Behaviour Science reported a significant association of anxiety and impulsivity with premature muzzle graying in young dogs.

Research on premature graying in humans has been extensive. Factors associated with premature graying in humans can be grouped into four major categories: oxidative stress, disease, work-related stress, and genetics. In particular, disease-based premature graying can occur when a stressful lifestyle lowers resistance to stress in the hair follicles and melanocytes. Regarding work-related stress, a heavy work load can place stressful demands on the body; these demands increase adrenaline production, which contributes to changes in hair color.

It is common for the hair along a dog’s muzzle line to turn gray with age. However, there has been minimal research on premature graying in dogs. In a review of case studies from an animal behavior practice, authors noted observations of young dogs (< 4 years old) with premature graying; many of these dogs demonstrated anxiety and impulsivity issues. Another study reported an association between certain behavioral measures, such as hiding or running away, and elevated cortisol levels in the hair of dogs; these cortisol levels reflected chronic emotional reactivity.

Prior studies have identified potential symptoms of canine anxiety and impulsivity. For example, an anxious dog may engage in stress whining or want to stay close to its owner. A dog with impulse issues may have difficulty focusing, bark endlessly, or be hyperactive.

For the current study, authors recruited dogs by posting flyers and speaking to dog owners at veterinary clinics, dog parks, and dog shows. Young dogs (1—4 years old) with hair color allowing for clear discernment of muzzle grayness were included. After excluding the dogs that did not meet inclusion criteria, 400 dogs (198 females, 202 males) were included in the study.

Dog owners were asked to complete a 42-item questionnaire including items assessing anxiety (whines or barks at the vet, is typically fearful) and impulsivity (leash pulling, persistent barking to gain attention). Authors added “distractor” questionnaire items so owners would not be able to determine the study’s purpose.

Authors took two photographs (front view, side view) of each dog. Two individuals not involved in data collection and without access to questionnaire responses independently rated each set of photographs using an ordinal rating scale: 0 (no gray), 1 (frontal gray), 2 (half gray), 3 (full gray).

Authors then used latent regression analysis to evaluate associations of anxiety and impulsivity with the extent of muzzle grayness. Ordinal regression analysis was used to identify associations of specific fear stimuli and other variables with muzzle grayness ratings. Control variables for each type of analysis were size, age, sex, neuter/spay status, and presence of medical problems.

Just over half (54%) of dogs exhibited muzzle grayness. There was a high inter-rater agreement for the ordinal ratings.

Latent regression analysis demonstrated a significant and positive association of anxiety and impulsivity with the extent of muzzle grayness. Among the control variables, age and sex were significantly and positively associated with the extent of muzzle grayness; specifically, higher levels of muzzle grayness were present in older dogs compared with younger dogs, and female dogs compared with male dogs. Interestingly, although female dogs and older dogs were more likely to have muzzle grayness, the positive association of anxiety and impulsivity with muzzle grayness was similar regardless of age and sex.

The five types of fear stimuli included in ordinal regression analysis were thunderstorms, loud noises, unfamiliar places, unfamiliar people, and unfamiliar animals. Of these, three (loud noises, unfamiliar animals, unfamiliar people) demonstrated significant and positive associations with muzzle grayness. The extent of muzzle grayness was greater in dogs having fear responses to these stimuli than those that did not have fear responses.

Authors also used ordinal regression analysis to evaluate data on the number of dogs and cats in the household, spent outside unsupervised, and participation in organized activity. None of these variables demonstrated significant associations with muzzle grayness.

Authors acknowledged that exclusion of dogs with white, gray, pale, or merled muzzles was a necessary limitation, making the study results applicable only to dogs with dark muzzles.

Given the study results, authors suggested incorporating muzzle grayness observations when assessing a dog for anxiety, impulsivity, or fear issues. Detection of premature graying could help veterinarians develop early intervention programs to effectively address and alleviate anxiety and impulsivity in dogs with these issues.

​Dr. JoAnna Pendergrass received her doctorate in veterinary medicine from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, LLC.