Concurrent Multidomain Cognitive Assessment and Serum BDNF Level in Aged Dogs: Comparison Between Normal Cognition and Mild Cognitive Impairment.

Early detection of canine cognitive dysfunction syndrome (CDS) is challenged by the limitations of single diagnostic tools, including owner-reported subjectivity and impractical behavioral testing protocols. This study examined a multidomain strategy integrating questionnaires, behavioral testing, and a circulating biomarker to identify measures associated with mild cognitive impairment in aged dogs. A total of 21 aged dogs were classified as cognitively normal (n = 9) or mildly cognitively impaired (n = 12) using the Canine Dementia Scale (CADES), and they were further assessed based on the Canine Cognitive Dysfunction Rating Scale (CCDR), a battery of behavioral tests across six cognitive domains, and serum brain-derived neurotrophic factor (BDNF) concentrations. The CADES scores differed significantly between the mildly cognitively impaired and cognitively normal groups (median 12.5 vs. 0, p < 0.01), whereas the CCDR scores did not (p = 0.114). Among the behavioral measures, the delayed match-to-sample task with a 20-s delay and the recognition index derived from novel object recognition testing were significantly associated with cognitive group classification; the other domains showed no significant associations. Serum BDNF concentrations did not differ between the groups or predict group membership. The results of this exploratory study show that targeted behavioral measures may be more strongly associated with mild cognitive impairment than circulating BDNF, thus supporting their potential utility for early cognitive screening in clinical settings. However, these findings should be interpreted with caution, and their diagnostic accuracy should be confirmed in larger cohorts with further validation.