Experiencing fear is not pleasant. Any human will tell you this. As one of our most basic emotions, fear functions as a rapid-fire means of communicating to our bodies “DANGER, DANGER – GET AWAY NOW!!”
As a physiological state, fear is associated with a set of bodily changes that are decidedly uncomfortable. Respiration and pulse increase, we become hyper-vigilant of our surroundings, our hearts pound, and we may experience a strong inclination to flee (especially considering that Tella Tubbies run really fast despite their portly dimensions).
Dogs who experience fear exhibit the same physiological signs as humans and most likely also suffer the same unpleasant emotional state. Common fears/anxieties in dogs include separation anxiety, fear of unfamiliar people or dogs, and sensitivity to thunder or loud noises. When these problems persist over long periods of time, they will definitely reduce a dog’s quality of life and can negatively affect the relationship between the dog and his or her owner. In addition, long-term exposure to stress may affect dogs’ physical health and longevity.
Background: There is evidence in humans and in laboratory species that experiencing prolonged periods of stress and anxiety increase an individual’s susceptibility to disease and risk of premature death (1-3). A possible underlying cause for this effect may be chronic activation of the hypothalamic-pituitary-adrenal [HPA] axis, which is part of the body’s natural defense against physical and psychological stressors. It is the HPA system that is responsible for elevated levels of cortisol, that well-known hormone that prepares one’s body for flight or fight. Although cortisol is highly effective in the short-term, prolonged exposure to high circulating levels is associated with a number of chronic health problems, such as hypertension, insulin resistance, heart problems and immune disturbances. Increased oxidative stress also occurs during exposure to physical or emotional stressors, and is associated with an increased rate of cellular aging and death. Although the exact underlying mechanisms are not fully understood, it is well-established that living in fear is not good for us.
What about dogs? Although the relationship between prolonged stress, health and lifespan is an active area of research in human subjects, until recently this association had not been studied in dogs.
The Study: Nancy Dreschel, a veterinarian at Pennsylvania State University, asked the question: “Are dogs who are more anxious or fearful at increased risk for health problems and a shortened life span?”(4). The study used a web-based questionnaire to collect information from people who owned a dog that had died within the previous five-year period. The survey included questions about the dog’s demographics, social environment, behavior, training history, health, and daily interactions with the owner. A set of questions adapted from the validated C-BARQ program was used to collect detailed information about the presence or absence of fear-related and anxious behaviors. Age and cause of death were also recorded. The survey was available on-line for 7 months and resulted in 721 complete surveys that were used in the analysis.
The Results: As expected, body size and weight were negatively correlated with lifespan. It is well-established that large/giant dogs have a shorter average life span than small and medium size dogs. In addition, neutered dogs had a longer lifespan than intact dogs and accidental deaths were associated with a younger age of death. When body size, neuter status, and accidental death were controlled for, several significant relationships were found between behavior and lifespan:
- A significant negative correlation was found between the fear of unfamiliar people and lifespan. This means that dogs who experienced a lifelong fear of strangers tended to die at a younger age than dogs who did not experience this type of fear. However, the earlier age of death in this subset of fearful dogs was not associated with any particular disease. (Because long-term activation of the HPA axis negatively affects the immune system, it was speculated that fearful dogs would be more susceptible to cancer, infections, or immune-mediated disorders. However, this relationship was not found in these data).
- The presence of non-social fears (fear of new places or things) and separation anxiety were both positively associated with chronic skin problems. The underlying mechanism might be the effects of long-term stress on the immune system and skin health, a relationship that has been reported in human subjects. However, this study’s design did not allow determination of causation, so conclusions regarding the underlying cause for this relationship could not be made.
- Lifespan was strongly and positively correlated with owner-reported “good” behavior. Dogs who were perceived as being well-behaved by their owner lived longer than those who were reported to be less well-behaved. Multiple factors may have been in play with this relationship. Because problem aggression was not specifically studied, euthanasia for aggression may have been a significant contributing factor. Less dramatically, owners who reported their dogs as less well-behaved may have been less bonded to the dog and more likely to euthanize at a younger age or to decline treatment for a serious illness. It is also possible that well-behaved dogs tend to live longer because they experience a less stressful and more harmonious home environment with their owner. Because none of these factors were studied separately, the exact cause or causes of this relationship could not be teased out, but certainly warrants additional study.
Take Away for Dog Folks: Remember that survey studies provide information through the eyes of the owner and, in this case, the collected data were also retrospective (historical) in nature. These factors must always be considered when making conclusions about survey studies. In addition, the statistical tests used in this study tell us if two or more factors are related (i.e. correlated), but cannot provide information about the direction of that relationship or if there is another underlying cause that was not identified. Even considering these limitations, the results of this study suggest that prolonged fear and anxiety not only impact a dog’s quality of life, but may also contribute to an early death and increased susceptibility to chronic health (skin) problems. Helping dogs to overcome fear is vital to improving their lives and our relationships with them. For those of you who are working with these dogs on a daily basis, thank you for all that you do (5).
References and Information Sources:
- Cavigelli SA, McClintock MK. Fear of novelty in infant rats predicts adult corticosteroid dynamics and an early death. Proceedings of the National Academy of Science USA 2003;100:16131-16136.
- McEwen BS. Stressed or stressed out? Journal of Psychiatric Neuroscience 2005; 30:315-318.
- Schultz R, Beach SR. Caregiving as a risk factor for mortality. Journal of the American Medical Association 1999; 282:2215-2219.
- Dreschel NA. The effects of fear and anxiety on health and lifespan in pet dogs. Applied Animal Behaviour Science 2010; 125:157-162.
- An excellent source of information for working with fearful dogs is Debbie Jacob’s book “Guide to Living With & Training a Fearful Dog and her blog, Fearful Dogs.