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A Dog's Mouth May Be the Key to Its Continuing Mental Health

In dogs the health of teeth and gums is related to canine cognitive dysfunction.

Key points

  • The canine equivalent to Alzheimer's disease is Canine Cognitive Disorder.
  • For humans some data suggests that periodontal disease may contribute to the onset of Alzheimer's disease.
  • New data shows that dogs with periodontal disease are more likely to suffer from the mental decline associated with Canine Cognitive Disorder.
Photo By Schankz on Vital Imagery
Source: Photo By Schankz on Vital Imagery

There are a lot of similarities between dogs and humans when it comes to age trends in their mental abilities. In general, both species show a decline in their cognitive abilities when they age, and both may experience severe forms of dementia when they are older. In humans the most frequently encountered age-related source of diminished mental ability is Alzheimer's disease. Older dogs can be affected by something very similar and it is called "Canine Cognitive Dysfunction" or CCD. Although the exact causes of these mental declines in the elderly are still under investigation, it is known that, in the brain, islands of dead and tangled connections, called beta-amyloid plaques, form and interrupt normal neural processing. The exact causes of these plaques are the focus of much research but probably involve some microbial agents.

Some recent research suggests that what is going on in an individual's mouth may play an important role. Specifically periodontal or gum disease has been shown to be an important factor in humans with Alzheimer's disease. Research suggests that these gum inflammations and the body's subsequent response to them are implicated as contributing to or perhaps even causing some of the damage associated with Alzheimer's. Recently Curtis Wells Dewey of Elemental Pet Vets in Freeville, New York, and Mark Rishniw of the College of Veterinary Medicine at Cornell University have provided data that suggests that what is going on in a dog's mouth may be similarly related to the mental problems associated with Canine Cognitive Dysfunction.

These researchers took measurements on 11 aging dogs (9 years or older) who had known CCD and a control group of 10 dogs of a similar age who were normal. Specifically, they took photographs of the mouths of all of these dogs. It is well-established that an estimate of periodontal or gum disease can be gotten by simple visual inspection of the mouth. The owners of both groups of dogs were also given a short questionnaire to allow a more detailed assessment of the appearance of symptoms.

The symptoms of Canine Cognitive Dysfunction are readily visible. Dogs with CCD seem to be disoriented, staring blankly at walls or into space, not recognizing familiar people, and even getting lost in the house or their own backyard. Social interactions are also diminished, and the dogs appear to be more anxious, less active, and emotionally reactive around visitors, family, or other pets in the house. In addition, their normal sleep cycle seems to be disrupted and they are more likely to wake at night and engage in pacing and restless behavior. Often they also begin to show house soiling and are less responsive to commands that they used to know well. Therefore a questionnaire measuring the presence of these symptoms completed by the owners of the dogs allows, not only the verification of whether the dogs had CCD or not but also the severity of the problem.

The photographs of the mouths of these dogs included pictures of the front and right and left sides of the mouth. These photographs were later given to 12 veterinarians who evaluated the sets of dental images and scored them for periodontal dental disease on a scale ranging from 0 to 4. The veterinarians doing the scoring had no idea as to the identity or actual diagnosis of any of the dogs that they were assessing.

The results were fairly straightforward. This study suggests that the older dogs with Canine Cognitive Dysfunction tended to show worse levels of periodontal disease than similarly aged dogs without CCD. Furthermore, the scores indicating the degree of cognitive dysfunction tended to correlate positively with the degree of gum disease. This seems to be in line with research on humans which showed that periodontal disease is a risk factor for the development of Alzheimer's disease.

Since this study is correlational in nature the researchers can't definitively decide whether the poor health status in a dog's mouth is an actual cause of Canine Cognitive Dysfunction or a contributory factor. Other research has suggested that keeping dogs physically and mentally active and adding antioxidants to their diet may help prevent CCD. Based on these new data, one might suggest that adding regular dental care might also be a useful protective measure against age-related mental decline. Given these current findings, it is certainly something that I would suggest.

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Curtis Wells Dewey and Mark Rishniw (2021). Periodontal disease is associated with cognitive dysfunction in aging dogs: A blinded prospective comparison of visual periodontal and cognitive questionnaire scores. Open Veterinary Journal, 11(2): 210–216, DOI: 10.5455/OVJ.2021.v11.i2.4

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