Assessment of severity and progression of canine cognitive dysfunction syndrome using the CAnine DEmentia Scale (CADES)

Cognitive dysfunction syndrome (CDS) represents a group of symptoms related to the aging of the canine brain. These changes ultimately lead to a decline of memory function and learning abilities, alteration of social interaction, impairment of normal housetraining, changes in sleep–wake cycle and general activity. The initial symptoms gradually worsen over time. Despite extensive research, little is known about the staging and phenotypic variability of CDS. We have analysed more than 300 dogs; 215 were selected for the study. We developed a rating scale, CADES – canine dementia scale – containing 17 items distributed into four domains, related to changes in dogs’ behaviour: spatial orientation, social interactions, sleep–wake cycles and house soiling. Using CADES, we identified various stages of cognitive impairment: mild cognitive impairment, moderate cognitive impairment and severe cognitive dysfunction. Further, we found that the rate of conversion at 6-months follow-up of normal ageing to mild cognitive impairment was 42%, while conversion rate of mild to moderate cognitive impairment was 24%. At twelve months, the conversion rates almost doubled to 71.45% and 50%, respectively. These findings showed that CADES can be used as a predictor of conversion from normal ageing to mild, and from mild to moderate cognitive impairment. In regards to the four behavioural domains we found that impairment in social interaction was frequently present in dogs with mild cognitive impairment (40%), 67% of dogs with moderate cognitive impairment had affected social interaction and sleep–wake cycles. For severe cognitive dysfunction, the majority of dogs displayed impairment in all four domains, while other two subgroups showed impairment only in three domains. In this study, we have assessed the psychometric properties of the CADES scale, and validated it as a screening tool for CDS. The scale is also suitable for long-term assessment of the progression of cognitive impairment in canines, and potentially as efficacy readout for treatments.