Evidence Update–Canine Cognitive Dysfunction

Canine Cognitive Dysfunction (CCD) is a common and significant disease in older dogs which resembles, in many ways, some forms of dementia in humans. I have written about proposed therapies several times (1, 2, 3). Because there is no highly effective therapy for this disorder, it is a condition for which many unproven treatments are marketed based almost entirely on anecdotes or theoretical rationale. A new study adds a little to our understanding of this disease
Fast, R., Schütt, T., Toft, N., Møller, A. and Berendt, M. (2013), An Observational Study with Long-Term Follow-Up of Canine Cognitive Dysfunction: Clinical Characteristics, Survival, and Risk Factors. Journal of Veterinary Internal Medicine, 27: 822–829. doi: 10.1111/jvim.12109

The study involved evaluating geriatric dogs presenting to a general practice for routine care or minor health problems and classifying them as having CCD, borderline CCD, or no evidence of CCD based on a questionnaire. The dogs were characterized by symptoms, breed, and potential risk factors and then followed for 3 years to determine survival to this point.

The authors identified four primary clinical symptoms most consistently present in CCD dogs- sleeping during the day and restless at night, altered interaction, signs of disorientation at home, and anxiety. They did not find that eliminating indoors was a common symptom, which is important since this is often intolerable to owners and leads to considerations of euthanasia.

Interestingly, they did not find a difference in 3-year survival between dogs with and without CCD. The dogs with CCD received active therapy (selegilene, therapeutic diets, and behavioral stimulation), which might have had an impact on their outcome, though it isn’t possible to say from these data.

Finally, the authors evaluated Vitamin E levels in the different groups since it is often hypothesized that oxidative damage plays a role in the disease, and some prior studies have found decreased vitamin E levels in the brains of dogs and humans affected by dementia. In this study, however, no association between CCD and Vitamin E level was identified.

As is always the case, there are a number of limitations to this study, in particular the potential bias in how subjects were selected and the lack of systematic control for potential differences between subjects other than CCD. It is essentially a descriptive study, and as such provides some information about the characteristics of this population, but it cannot be used to draw definitive conclusions about the cause or treatment of CCD.