Higher burden of neuropsychiatric symptom-like behaviors associated with canine cognitive dysfunction compared to normal aging in the Dog Aging Project.

Non-cognitive, neuropsychiatric symptoms (NPS) are nearly universal in Alzheimer's disease (AD), but investigation of their underlying biology is complicated by comparative medicine approaches that incompletely capture spontaneous disease, primarily using transgenic rodent models. The aged companion dog, which spontaneously develops an AD-like disease called canine cognitive dysfunction (CCD), may help fill this translational gap. Using data from the Dog Aging Project with > 10,000 aged dogs (> 8 years old), we identify numerous behaviors in dogs "at-risk" for and with CCD that mirror NPS in humans. Compared to dogs without CCD, our analysis shows that dogs with CCD are less physically active, exhibit fewer previously trained behaviors, demonstrate fewer motivated behaviors, have more daytime sleep, demonstrate more separation anxiety, have altered anxious responses to novelty, have changes in aggressive behaviors, and exhibit lower appetite. Using k-means clustering, we did not find evidence for behavioral sub-phenotypes. Overall, our analysis of a large number of aged dogs suggests clinically significant NPS are associated with CCD and that the companion dog may serve as an important comparative medicine approach to understand these debilitating symptoms across species.