An exploratory study of behavioral, cognitive, physiological, and microbiota profiles in senior dogs

Introduction: Aging in dogs is a multifactorial process involving behavioral, cognitive, immunological, and microbiota-related changes, yet distinguishing healthy from pathological aging remains challenging. This exploratory study aimed to evaluate physiological indicators of health by integrating pain evaluation and cognitive testing in senior companion dogs. Methods: Eighteen companion dogs aged ≥8 years underwent standardized behavioral and cognitive evaluations (Mini C-BARQ, DISHAA, object choice test), chronic pain assessment (Helsinki Chronic Pain Index), and quality-of-life (QoL) scoring. Hematological parameters, serum brain-derived neurotrophic factor (BDNF), and Th1/Th2 ratios were measured as physiological indicators, while fecal samples were analyzed via 16S rRNA sequencing for microbiota profiling. Results: All dogs scored above the chronic pain threshold (mean HCPI: 28.72), although caregiver-reported QoL ratings suggested good overall wellbeing. Cognitive testing yielded low average scores on the DISHAA (mean: 9.05), with only one dog showing mild cognitive decline; however, mean performance on the object choice test was low (1.94/5). Mean serum BDNF concentration was 0.154 ng/dL (SD: 0.082) and correlated positively with red blood cell (RBC) count and negatively with MCV, MCH, and MCHC (p ≤ 0.05). Immune profiling patterns suggested Th2 polarization. The gut microbiota was dominated by Firmicutes and Bacteroidetes. Principal Component Analysis (PCA) identified two primary dimensions of biological variation: a pain–immune–microbiota axis, defined by higher chronic pain scores, Th2 polarization, increased Prevotella abundance, and higher DISHAA scores, and a second component reflecting microbiota compositional variation. Discussion: These preliminary findings highlight potential interactions between pain, microbiota composition, and immune dysregulation, suggesting their possible utility as candidate indicators for differentiating healthy from pathological aging in dogs.